Internal  Combustion  Engine  Manual 


INTERNAL  COMBUSTION  ENGINE 

MANUAL . 


BY 

F.    W.    STERLING 
Lieutenant,  U.  S.  Navy 


ANNAPOLIS,    MARYLAND 

SCHOOL  OF  MARINE  ENGINEERING 

U.  S.  NAVAL  ACADEMY 

1911 


COPYRIGHT,    IQII 

BY 
F.    W.    STERLING 


BALTIMORE,  MD.,  U.  8.  A. 


FOREWORD. 

In  an  effort  to  present  briefly  and  clearly  the  Internal  Combus- 
tion Engine  problem  to  the  uninitiated,,  the  author  has  compiled 
the  data  in  this  volume.  It  has  been  the  endeavor  to  eliminate  all 
obsolete  practice,  to  put  forth  the  best  modern  practice,  and  to 
illustrate  all  points  by  up-to-date  commercial  examples. 

After  close  stud}^  of  the  conditions  existing  in  the  Internal 
Combustion  Engine  course  at  the  U.  S.  Naval  Academy,  and  after 
voluminous  reading  to  discover  the  best  general  method  of  present- 
ing the  subject,  the  following  was  thought  the  best  sequence  to 
follow : 

(a)  The  subject  of  fuels  is  first  treated  fully,  this  being  the 
fundamental  element  that  governs  design  and  operation.     These 
fuels  follow  in  a  natural  sequence  which  order  is  preserved  when 
carburetion  is  taken  up  in  Chapter  V. 

(b)  The  engine  proper  naturally  divides  itself  into  four  sys- 
tems: (1)  fuel  system,  (2)  ignition  system,  (3)  cooling  system,  (4) 
lubrication  system.     These  are  treated  in  detail  in  the  above  order 
and  in  Chapter  X  the  four  systems  assembled  are  illustrated  by 
modern  commercial  engines. 

(c)  Producer  plants  being  closely  allied  to  gas  engines  are  given 
a  short  chapter  at  the  end  of  the  book. 

This  volume  being  primarily  intended  as  a  text-book  for  mid- 
shipmen is  necessarily  limited  in  its  scope  by  the  time  allowed  for 
this  course  in  the  Naval  Academy  curriculum.  This  necessitates 
brevity  and  is  responsible  for  many  arbitrary  statements  contained 
herein.  The  endeavor  has  been  to  limit  these  to  the  closest  approxi- 
mation to  the  best  practices  where  fuller  explanation  would  extend 
the  book  to  impossible  limits. 

The  author  wishes  to  thank  the  various  manufacturers  for  the 
illustrations  used  in  Chapter  X,  and  the  Hill  Publishing  Company 
for  permission  to  reproduce  some  of  the  figures  in  Chapter  XI. 


268688 


CONTENTS 

CHAPTER  PAGE 

1.  FUELS    1 

2.  GENERAL    15 

3.  CONSTRUCTION    23 

4.  TYPES,  CYCLES,  ETC 34 

5.  CARBURETION,  THE  MIXTURE,  ITS  PREPARATION,  CARBURETERS  AND 

VAPORIZERS    42 

6.  IGNITION    52 

7.  COOLING  AND  LUBRICATION 64 

8.  GOVERNING  AND  INDICATOR  CARDS 69 

9.  EFFICIENCY,  MANAGEMENT,  OPERATION,  DEFECTS  AND  REMEDIES  . .  82 

10.  ENGINES 94 

11.  GAS  PRODUCERS  .                                                                                  .  126 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


CHAPTER  I 
FUELS 

The  considerations  governing  the  selection  of  a  fuel  in  general 
are  its  accessibility,  price,  amount  available,  rate  of  combustion,  and 
thermal  value;  it  does  not  naturally  follow  that  these  are  the  only 
limitations  which  shall  regulate  the  choice  of  a  fuel  for  use  in  an 
internal  combustion  engine.  This  being  a  specific  form  of  engine 
requires  special  consideration. 

Fuel  for  use  in  an  internal  combustion  engine  must  readily  com- 
bine with  air  to  form  a  combustible  mixture  of  gas  or  vapor,  must 
leave  little  or  no  solid  residue  after  combustion,  and  must  have  cer- 
tain thermo-chemical  characteristics  such  as  a  proper  rate  of  flame 
propagation,  etc.  It  need  not  necessarily  be  of  a  very  high  calorific 
value,  as  will  be  shown  later,  but  obviously  this  is  desirable.  The 
fuel  is  usually  a  compound  of  carbon  and  hydrogen,  or  a  mixture 
of  such  compounds,  found  thus  in  nature  or  manufactured. 

The  general  classification  of  internal  combustion  engine  fuels  is : 

1.  The  solid  fuels. 

2.  The  liquid  fuels. 

3.  The  gaseous  fuels. 

Solid  fuels  cannot  be  used  in  an  internal  combustion  engine  in 
their  natural  state,  hence  coal  and  other  carbonaceous  solids  must 
be  gasified  to  CO  and  H  by  partial  combustion  and  volatilization  to 
prepare  them  for  such  use.  Although  the  Diesel  engine  was  origi- 
nally designed  to  use  coal  dust  for  fuel,  and  experiments  have  been 
made  along  this  line,  the  idea  was  finally  abandoned. 

Solid  fuels  are  converted  into  (a)  air  gas,  (b)  water  gas,  (c) 
producer  gas. 

Liquid  fuels  comprise  (a)  distillates  of  petroleum  or  crude  oil, 
and  (b)  alcohol. 


2  INTERNAL  COMBUSTION  ENGINE  MANUAL 

The  gaseous  fuels  consist  of  (a)  oil  gas,  (b)  illuminating  gas, 
(c)  coke  oven  gas,  (d)  blast  furnace  gas,  (e)  natural  gas,  and  (f ) 
acetylene. 

Of  all  these  fuels  the  most  important  from  the  marine  standpoint 
is  petroleum. 

1.  Solid  Fuels 
A.  AIR  GAS 

Although  entitled  to  no  commercial  consideration  because  of  its 
rarity,  air  gas  must  be  mentioned  here  as  a  possible  fuel.  It  can  be 
manufactured  by  the  gasification  of  carbon  by  incomplete  combus- 
tion to  CO  in  a  producer. 

The  complete  combustion  to  C02  of  1  pound  of  carbon  would  gen- 
erate 14,650  B.  T.  U.  Partial  combustion  to  CO  of  the  same  carbon 
would  liberate  about  4430  B.  T.  U.  Therefore,  if  this  CO  could 
be  led  from  the  producer,  it  would  be  a  gaseous  fuel  containing 
10,220  B.  T.  U.  per  pound  of  carbon.  Since  each  pound  of  carbon 
is  combined  with  1^  pounds  of  0  when  the  CO  is  formed,  the  gas 
contains  10,220  B.  T.  U.  per  2J  pounds,  or  about  4380  B.  T.  U.  per 
pound  of  gas.  Of  course  this  is  an  ideal  condition  impossible  of 
attainment  by  any  commercial  apparatus  on  the  market. 

B.  WATER  GAS 

If  incandescent  fuel  is  sprayed  with  water  vapor,  the  H20  is 
dissociated  to  H2  and  0,  and  the  latter  combines  with  the  carbon 
in  the  fuel  to  form  C02  or  CO.  H2  is  liberated.  At  temperatures 
below  1250°  F.,  C02  is  formed,  whereas,  if  the  temperature  be  above 
1800°  F.,  CO  alone  is  formed. 

The  reactions  are: 

Below  1250°  C2  +  4=H20  =  2C02  +  4:H2.  (1) 

Above  1800°  C2  +  2H20  =  2CO  +2H2.  (2) 

By  formula  (2)  it  is  found  that  the  gas  formed  by  1  pound  of 
carbon,  when  converted  into  CO  and  H2  by  this  method,  will  con- 
tain 20,742  B.  T.  U.,  or  about  8300  B.  T.  U.  per  pound  of  gas. 


FUELS  3 

When  converted  by  formula  (1),  1  pound  of  gas  will  contain  55378 
B.  T.  U. 

From  these  figures  it  might  appear  that  this  were  an  efficient  gas 
production;  on  the  contrary,  water  gas,  reckoned  on  the  basis  of 
coal  used,  is  not  highly  efficient  for  the  following  reason:  starting 
with  a  fuel  in  the  incandescent  state,  the  continued  introduction  of 
water  vapor  will  cool  the  producer  and  when  the  temperature  falls 
below  1800°  F.  an  excessive  amount  of  CO 2  is  formed.  Unless 
some  means  is  devised  to  counteract  this  cooling  action  the  process 
will  finally  cease.  Practical  generation  of  water  gas  is  accomplished 
in  a  producer.  When  the  temperature  becomes  too  low  the  steam 
is  shut  off  and  the  fuel  is  again  brought  to  incandescence  by  blowing 
through  with  air.  During  this  "  blowing  up  "  process  gas  of  a  low 
grade  is  formed.  This  is  rarely  utilized  and  here  we  find  the  im- 
portant loss  which  accounts  for  the  low  efficiency  of  water  gas  as 
calculated  upon  the  basis  of  coal  consumed. 


c.  PRODUCER  GAS 

Producer  gas  is  formed  by  blowing  a  mixture  of  water  vapor  and 
air  through  a  bed  of  incandescent  fuel.  Thus  it  is  a  combination  of 
the  two  previous  gases.  Gas  producers  for  the  generation  of  this 
gas  have  reached  a  high  degree  of  perfection  and  hold  a  large  com- 
mercial field.  They  are  used  extensively  in  stationary  gas  engine 
plants  and  in  a  few  instances  have  been  adapted  to  marine  use. 
As  their  importance  justifies  a  chapter  on  the  subject,  it  will  be 
treated  later.  The  scope  of  this  work  prohibits  the  computation, 
but  it  can  be  shown  that  the  theoretical  product  of  a  gas  producer 
contains  about  14,000  B.  T.  U.  per  pound  of  carbon  consumed. 

In  these  discussions  of  the  three  classes  of  gas  formed  from  solid 
fuels  the  B.  T.  U.  per  pound  of  carbon  have  been  shown.  This 
gives  an  idea  of  their  thermal  value  based  upon  the  amount  of  solid 
fuel  used  and  must  not  be  confused  with  their  relative  thermal 
values  per  cubic  foot  of  gas.  It  must  be  borne  in  mind  that  all  the 
figures  are  theoretical. 


4  INTERNAL  COMBUSTION  EXGIXE  MAXUAL 

2.  Liquid  Fuels 
A.  PETROLEUM  AND  ITS  DISTILLATES 

By  far  the  most  important  fuels  for  marine  internal  combustion 
engines  are  derived  from  petroleum.  This  important  product  is 
found  in  nearly  every  part  of  the  globe.  The  United  States  and 
Russia  produce  most  of  the  petroleum  at  present.  In  this  country 
the  fields  of  Pennsylvania,  Ohio,,  Oklahoma,  Texas  and  California 
are  the  best  producers. 

Contrary  to  the  popular  idea,  oil  is  not  necessarily  found  in  the 
vicinity  of  coal  fields,  but  near  salt  deposits,  the  formation  of  salt 
and  oil  being  apparently  simultaneous.  Although,  still  open  to 
dispute,  it  appears  to  be  fairly  well  established  that  petroleum  was 
formed  by  the  decomposition  of  large  masses  of  organic  matter, 
probably  of  marine  origin,  and  the  subsequent  spontaneous  dis- 
tillation of  the  hydrocarbons  from  such  matter.  Some  few  petro- 
leums seem  to  be  of  vegetable  origin. 

One  of  the  most  interesting  experiments  in  support  of  this  organic 
theory  of  the  origin  of  petroleum  was  conducted  by  Engler.  He 
distilled  menhaden  (fish)  oil  between  the  temperatures  of  320°  C. 
at  10  atmospheres  pressure  and  400°  C.  at  4  atmospheres  pressure, 
resulting  in  60  per  cent  of  distillate,  having  a  specific  gravity  of 
0.81.  The  residue  contained  some  unsaponifiable  fat.  Fractiona- 
tion  of  the  distillate  showed  the  presence  of  members  of  the  hydro- 
carbon group  ranging  from  pentane  to  nonane,  and  finally,  a  light- 
ing oil  was  separated  which  was  indistinguishable  from  commercial 
kerosene. 

As  found  in  its  natural  state  its  composition  varies  with  the 
field  of  supply,  but  in  every  case  consists  of  (7  and  H  with  a  small 
amount  of  0  and  impurities,  the  average  for  13  fields  being  0  84 
per  cent,  JET  13.5  per  cent,  0  and  impurities  2.5  per  cent.  The 
greatest  variation  from  this  in  any  one  field  is  2.5  per  cent  C.  Its 
specific  gravity  (considering  only  those  fields  of  commercial  value) 
varies  from  0.826  found  in  a  Pennsylvania  field  to  0.956  found  in 
the  Baku  region.  A  field  in  Kaduka,  Eussia,  yields  a  crude  oil  with 
the  low  specific  gravity  of  0.65,  and  in  Mexico  an  oil  is  obtained 
with  the  high  specific  gravity  of  1.00. 


FUELS  5 

Petroleum  products  are  obtained  by  what  is  -known  as  fractional 
distillation.  The  fractionation  is  conducted  as  follows : 

The  horizontal  still  shown  in  Fig.  1  may  be  charged  with  600 
barrels  of  petroleum.  A  fire  is  built  on  the  grate  and  when  the  oil 
is  sufficiently  heated,  shown  by  an  even  ebullition,  superheated 


FIG.  1. — American  Horizontal  Cylindrical  Still. 

steam  is  introduced  to  the  still,  and  distillation  commences.  A 
temperature  of  130°  to  200°  C.  is  maintained  in  the  still  and  all 
the  kerosene  and  less  volatile  products  are  distilled  off,  passing  to 
the  deflegmator  on  the  still  head,  Fig.  2.  This  acts  as  a  separator, 
returning  any  oil  which  is  mechanically  carried  over  to  the  still, 
through  the  pipe  a.  From  the  deflegmator  the  distillate  passes  to 
the  condenser.  As  the  process  progresses,  the  temperature  is  raised 
to  250°  to  300°  C.  and  at  this  temperature  the  lubricating  fractions 
2 


6  INTERNAL  COMBUSTION  ENGINE  MANUAL 

are  obtained.  These  temperatures  vary  with,  the  petroleum  being 
distilled  and  with  the  form  of  still  used.  The  residue  contains 
cylinder  oil  and  greases.  These  three  fractions  are  usually  ob- 
tained at  the  first  distillation.  By  the  use  of  superheated  steam  the 
high  temperature  necessary  for  distillation  is  obtained  at  a  lower 
pressure  than  would  be  the  case  in  simple  distillation,  and  the  steam 
carries  the  vapors  away  to  the  condenser  as  fast  as  they  are  gen- 
erated, the  injury  to  the  products  resulting  from  their  remaining  in 


FIG.  2. — Deflegmator. 

contact  with  the  highly  heated  surface  of  the  still  thus  being  pre- 
vented. 

To  obtain  the  commercial  products  a  second  distillation  of  these 
fractions  is  necessary.  Eedistillation  of  the  first  fraction  gives 
petroleum  ether,  gasoline,  benzine,  naphtha  and  kerosene.  Redistil- 
lation of  the  residue  gives  cylinder  oil,  vaseline  and  residuum. 

The  products  obtained  are  not  in  a  marketable  condition  until 
chemically  treated  to  remove  impurities.  The  water  present  is 
settled  out.  In  the  case  of  lubricating  and  heavier  oils,  steam  coils 
in  the  settling  tanks  aid  this  settling  process  by  temporarily  re- 


FUELS  7 

ducing  the  viscosity  of  the  oil.  After  the  water  is  removed,  the 
distillate  is  treated  with  sulphuric  acid  followed  by  soda  lye.  The 
rationale  of  this  treatment  is  not  fully  understood,  but  the  action 
appears  to  consist  of  the  removal  or  decomposition  of  the  aromatic 
hydrocarbons,  acids,  phenols,  tarry  products,  sulphur,  etc.,  the  acid 
removing  some,  while  the  caustic  soda  removes  the  remainder  and 
neutralizes  the  acid  left  in  the  oil. 

During  the  purification  process  the  oil  is  agitated  by  mechanical 
apparatus  or  by  air  blast  to  aid  the  chemical  action.  After  settling 
in  tanks  the  commercial  products  are  ready  for  delivery.  These 
remarks  are  of  necessity  very  general,  as  the  processes  vary  in  the 
different  refineries.  The  principles,  however,  are  the  same  in  all 
cases.  Instead  of  introducing  superheated  steam  into  the  still,  the 
still  may  be  kept  at  a  low  pressure  by  the  "vacuum  process"  of 
distillation.  In  this  case  the  petroleum  is  distilled  under  a  partial 
vacuum  which  is  obtained  by  an  ejector  form  of  exhauster,  or  by 
designing  the  still  with  a  long  vertical  exhaust  pipe  running  down- 
ward from  the  still.  Condensers  are  of  various  types,  the  com- 
monest being  of  the  coil  type.  The  distillate  is  carried  through  a 
spiral  or  parallel  tube  coil  of  large  condensing  surface,  the  coil  be- 
ing cooled  by  water  circulated  around  it. 

"  Cracking."  The  "  cracking  process/'  which  was  an  accidental 
discovery,  revolutionized  the  method  of  kerosene  production.  It  is 
generally  employed  to  increase  the  production  of  kerosene  from  a 
given  amount  of  petroleum.  It  is  now  generally  understood  that  the 
products  of  fractional  distillation  are  not  identical  with  the  hydro- 
carbons in  the  crude  oil,  but,  in  part,  are  the  result  of  chemical  re- 
action during  distillation.  During  the  redistillation  of  the  fraction 
containing  lubricating  oil,  etc.,  the  temperature  is  carried  higher 
than  the  normal  boiling  point  of  kerosene.  The  result  of  this  is 
that  the  heavier  oil  undergoes  a  partial  dissociation  into  specifically 
lighter  hydrocarbons  of  lower  boiling  points.  These,  when  con- 
densed, form  a  commercial  kerosene. 

Temperatures  at  which  the  Fractions  Distill.  If  the  process  were 
carried  out  in  a  laboratory  to  obtain  the  distillation  temperatures 


8 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


of  the  different  petroleum  products  the  results  would  be  somewhat 
as  shown  in  the  table  below : 


Temp. 
(Fahr.) 

Distillate. 

Per  cent. 

Specific 
gravity.* 

Flash  point.* 
(Fahr.) 

113  140° 

Trace 

g 

140-160 

Gasoline                 )  commercial 

{2 

.65 

10 

160-250 
260-350 
350 

Benzine,  naphtha  v               gasoline.. 
Kerosene,  light.  .  \ 

10 
10 
35 

.70 
.73 

80 

14 
50 
150 

400 

Kerosene  heavy  

10 

.89 

270 

482 

10 

905 

315 

Cylinder  oil  

5 

.915 

360 

2 

.925 

Residue  

16 

100 

*  Approximately  mean  values. 

The  nomenclature  applied  to  the  petroleum  products  throughout 
the  world  is  so  varied  as  to  become  confusing,  benzine,naphtha,  gaso- 
line and  kerosene  being  used  very  indiscriminately.  For  simplicity 
we  might  divide  those  products  used  in  the  internal  combustion 
engine  as  fuel  into  (1)  commercial  gasoline  and  (2)  kerosene  and 
the  heavier  petroleum  distillates. 

1.  COMMERCIAL  GASOLINE 

All  figures  relative  to  the  boiling  point,  specific  gravity,  composi- 
tion, etc.,  must  be  comparative,  for  naturally  the  product  varies 
with  the  field  of  production  of  the  original  crude  oil.  Approxi- 
mately the  range  of  distillation  temperatures  for  commercial 
gasoline  is  115°  to  350°.  At  the  lower  temperature  gasoline  is 
distilled  off,  then,  as  the  temperature  is  increased,  follow  benzine, 
naphtha  and  light  kerosene  in  the  order  named.  Commercial  gaso- 
line may  contain  any  or  all  of  these  fractions.  Its  specific  gravity 
varies  from  0.65  to  0.75,  depending  upon  the  proportions  of  C  and 
H  in  its  composition  and  it  weighs  about  5.9  pounds  per  gallon. 
The  analysis  of  an  ordinary  sample  shows  G  85  per  cent,  H  14.8 
per  cent,  impurities  (principally  0)  0.2  per  cent.  Its  thermal 
value  is  roughly  20,000  B.  T.  U. 

The  standard  test  for  commercial  gasoline  is  its  specific  gravity. 
Obviously  this  criterion  is  erroneous  as  the  ultimate  value  of  gaso- 


FUELS  9 

line  as  a  fuel  depends  upon  its  volatility.  For  instance,  a  high- 
speed engine  needs  a  light  fuel,  easily  volatilized,  while  a  heavy 
duty,  slow-speed  motor  can  use  a  much  heavier  fuel.  Were  the 
entire  supply  of  gasoline  derived  from  one  field,  fractions  obtained 
at  the  same  temperatures  would  always  have  the  same  composition 
and  hence  the  same  specific  gravity.  But,  as  the  world's  supply  is 
obtained  from  many  fields  in  which  the  compositions  vary,  it  is  pos- 
sible to  obtain  two  gasolines  of  widely  differing  specific  gravities, 
which  would  distill  at  the  same  temperature  and  which  might  be 
of  equal  value  as  fuels.  The  volatility  of  two  gasolines  being  equal, 
the  heavier  is  more  efficient  due  to  the  presence  of  a  higher  per- 
centage of  carbon.  This  might  appear  paradoxical  from  the  thermal 
view,  but  is  based  upon  thermo-chemical  considerations. 

At  present  gasoline  holds  the  internal  combustion  engine  field 
as  the  most  important  of  the  petroleum  products.  To  prepare  gaso- 
line for  combustion  it  must  be  vaporized,  and  the  ease  with  which 
this  is  accomplished  gives  it  a  decided  advantage  over  all  other 
liquid  fuels.  This  fuel  is  vaporized  or  volatilized  by  passing  air 
over  or  through  the  liquid,  or  by  spraying  the  liquid  into  the  air 
by  force  or  suction.  This  process,  called  carburetion,  will  be  treated 
in  a  later  chapter. 

2.  KEROSENE 

The  next  heavier  distillate  after  gasoline  is  kerosene.  This  is 
given  off  at  350°  F.  to  400°  F.  and  has  a  specific  gravity  ranging 
from  0.78  to  0.82.  The  composition  of  a  test  sample  might  run 
0  85.1  per  cent,  H  14.2  per  cent,  0  0.7  per  cent.  Its  heating  value 
is  about  20,000  B.  T.  U.  and  its  flash  point  is  between  100°  F.  and 
125°  F.  It  is  safer  to  handle  and  stow  than  gasoline,  and  being  less 
volatile  does  not  deteriorate  so  rapidly. 

It  is  not  so  widely  used  as  an  internal  combustion  engine  fuel 
as  is  gasoline,  for  at  ordinary  temperatures  it  does  not  form  an 
explosive  mixture  with  air,  and  to  render  it  a  suitable  combustible 
requires  special  treatment,  such  as  introduction  into  a  heated  vapor- 
izer, or  spraying  into  a  heated  cylinder.  This  will  be  treated  at 
length  under  carburetion.  The  introduction  by  one  of  the  popular 


10  INTERNAL  COMBUSTION  ENGINE  MANUAL 

motor-car  makers  of  a  carbureter  which  will  handle  either  gasoline 
or  kerosene  may  do  much  to  bring  it  before  the  layman. 

1.  The  Heavier  Distillates.     Fuel  oils  have  a  specific  gravity  of 
0.80  to  0.89  being  of  a  thick  consistency,  have  a  high  flash  point, 
and  have  a  heating  value  of  17,000  to  19,000  B.  T.  IT.    This  is  the 
fuel  used  in  what  are  known  as  oil  engines.     It  must  be  sprayed 
into  the  hot  cylinder  or  vaporized  in  a  heated  vaporizer.     Heat  is 
imperative  for  its  conversion  to  vapor  as  it  will  not  form  a  com- 
bustible vapor  at  ordinary  temperatures. 

2.  Crude  Oil.     Crude  oil  is  the  same  thing  as  petroleum  and  has 
been  described  under  that  head.    It  is  used  in  some  motors,  notably 
the  Diesel  engine,  by  spraying  it  into  the  cylinder  which  is  partially 
filled  with  heated  highly  compressed  air. 

B.  ALCOHOL 

Although  there  are  over  twenty  compounds  known  to  the  chemist 
as  alcohols,  the  most  important  as  a  fuel  is  ethyl  alcohol,  expressed 
by  the  formula  C2H5OH.  Being  a.  fixed  compound  its  character- 
istics cannot  vary  as  in  the  case  of  petroleum  products.  Abso- 
lute alcohol,  that  is  100  per  cent  pure,  has  a  specific  gravity  of 
0.7946  at  15°  C.  and  1  gallon  weighs  6.625  pounds.  Its  great 
affinity  for  water  militates  against  the  commercial  article  being 
very  pure. 

Until  a  few  years  ago,  a  high  internal  revenue  on  the  manu- 
facture of  the  article  prohibited  its  use  as  a  fuel  in  this  country. 
Congress  then  removed  the  revenue  upon  the  article  if  "  denatu- 
rized  "  and  it  is  now  beginning  to  take  its  legitimate  place  in  the 
fuel  field.  This  denaturizing  process  consisted  of  adding  to  the 
ethyl  spirit  a  fixed  amount  of  methyl  or  wood  alcohol  to  render  it 
undrinkable,  and  a  small  percentage  of  benzine  to  prevent  the  re- 
distillation of  the  'ethyl  spirits.  Congress  prescribed  the  following 
formula :  100  volumes  90  per  cent  ethyl  alcohol,  10  volumes  90 
per  cent  methyl  alcohol,  and  J  volume  approved  benzine.  Benzine 
raises  the  thermal  value  of  the  mixture.  One  of  the  denaturizing 
agents  required  by  the  laws  of  some  countries  is  benzol.  This 
benefits  the  fuel  by  neutralizing  the  formation  of  acetic  acid  in  the 
cylinder  during  combustion. 


FUELS  11 

As  noted  above,  alcohol  is  rarely  found  free  from  water  and  is 
therefore  designated  by  its  percentage  of  purity,  thus,  "90  per 
cent  alcohol "  indicates  the  presence  of  10  per  cent  water.  Pure 
alcohol  has  a  thermal  value  of  about  11,660  B.  T.  U.  and  of  course 
the  presence  of  water  reduces  this  value.  From  this  it  might  be 
erroneously  concluded  that  its  thermal  efficiency  as  an  internal 
combustion  engine  fuel  is  lower  than  that  of  gasoline.  On  the 
contrary  its  thermal  efficiency  is  higher,  as  alcohol  can  be  more 
highly  compressed,  and  the  dissociation  of  its  contained  water  seems 
to  aid  the  expansion  stroke.  If  equal  weights  of  petroleum  and 
alcohol  are  completely  burned  in  two  motors,  the  latter  will  require 
less  air  than  the  former,  and  consequently  the  heat  losses  in  the  ex- 
haust gases  are  less  per  pound  of  fuel  in  the  alcohol  motor.  An 
average  thermal  efficiency  of  gasoline  in  a  motor  is  about  15  per 
cent.  The  thermal  efficiency  of  alcohol  under  some  test  conditions 
has  reached  28  per  cent  and  30  per  cent.  The  principal  cause  of 
this  greater  efficiency  is  the  higher  compression  permissible.  These 
are  extreme  cases,  however,  and  must  not  be  taken  as  criterions. 

Alcohol  is  less  volatile  than  gasoline  and  is  easier  to  handle  than 
kerosene.  It  requires  a  special  form  of  vaporizer  for  it  will  not 
form  a  combustible  mixture  with  air  at  ordinary  temperatures. 
Heat  is  employed  to  aid  in  its  vaporization  as  will  be  shown  under 
carburetion.  When  the  cost  of  alcohol  is  sufficiently  reduced,  and 
this  time  is  in  sight,  it  will  compete  advantageous^  with  gasoline. 

3.  The  Gaseous  Fuels 
A.  OIL  GAS 

Gas  is  generated  by  vaporizing  crude  oil  by  one  of  two  distinct 
methods,  (1)  the  Pintsch  method,  and  (2)  the  Lowe  process.  At 
present  it  is  used  more  extensively  as  an  illuminating  gas  than  as 
a  gas  engine  fuel.  It  is  largely  employed  for  municipal  lighting, 
and  everybody  is  familiar  with  the  Pintsch  light  of  railroad  cars. 

1.  By  the  Pintsch  method  oil  is  led  through  a  retort  which  is 
externally  heated.  A  thin  film  of  oil  is  kept  in  contact  with  the 
heated  surface  and  is  thus  volatilized  into  a  fixed  gas.  It  varies 
considerably  in  composition  depending  upon  the  original  crude  oil, 


12  INTERNAL  COMBUSTION  ENGINE  MANUAL 

being  a  mixture  of  hydrocarbons  and  free  hydrogen.  Giilder  gives 
one  formula  17.4  per  cent  C2H^  58.3  per  cent  CH±,  24.3  per  cent 
H  by  volume. 

2.  The  Lowe  process  employs  a  fire-brick  lined  furnace  contain- 
ing a  checker  board  form  of  grating  made  of  fire  brick.  This  grat- 
ing is  heated  to  a  very  high  temperature  by  an  oil-air  blast.  When 
the  desired  temperature  is  reached,  the  blast  is  shut  off  and  the 
chimney  is  closed.  An  intimate  mixture  of  crude  oil  and  super- 
heated steam  is  now  sprayed  on  to  the  hot  grate  and  (air  being  ex- 
cluded) this  mixture  is  volatilized  into  an  oil-water  gas.  The 
grate  must  be  reheated  periodically.  The  analogy  to  the  manufact- 
ure of  water  gas  is  apparent.  In  addition  to  the  hydrocarbons  gen- 
erated by  the  Pintsch  method  we  have  Nf  0  and  00  in  small 
quantities  in  gas  made  by  this  method. 

The  process  of  generation  being  completed  by  either  method,  the 
resulting  product  is  washed,  scrubbed  and  purified  by  the  usual 
method  (see  gas  producers).  Although  the  heating  value  per  cubic 
foot  of  Pintsch  gas  is  nearly  40  per  cent  greater  than  that  made  by 
the  Lowe  process,  if  based  upon  fuel  consumption  required  for 
manufacture,  their  thermal  values  are  nearly  equal. 

B.  ILLUMINATING  GAS 

This  gas  is  a  mixture  of  H,  CO,,  CH±  and  other  heavy  hydro- 
carbons, 0,  N  and  CO,  given  up  by  bituminous  coal  when  it  is 
heated  in  a  retort,  air  being  excluded.  The  residue  is  coke,  tar  and 
ammonia  liquor.  Part  of  this  coke  can  be  utilized  to  heat  the 
retort.  One  ton  of  coal  will  give  off  about  10,000  cubic  feet  of  gas. 
Its  composition  necessarily  varies  widely,  dependent  upon  the  coal 
used  and  the  temperature  of  volatilization.  Its  heating  value,  which 
varies  with  the  composition,  is  about  600  B.  T.  U.  per  cubic  foot. 

c.  COKE  OVEN  GAS 

When  coal  is  coked  in  a  retort  the  resultant  volatile  products  are 
similar  to  illuminating  gas.  Hiscox  says  "in  the  Connellsville 
District  about  300,000  tons  of  coal  are  coked  per  week.  The  sur- 
plus gas  from  the  coal  would  develop  366,000  effective  horse-power 


FUELS  13 

continuously."  As  this  gas  is  suitable  for  gas  engine  use  the  great 
possibilities  of  developing  industries  utilizing  gas  engine  power 
cannot  long  go  unrecognized  in  districts  where  coking  is  carried  on. 
Modern  generation  of  illuminating  and  fuel  gas  may  be  illus- 
trated by  the  practice  of  the  United  Coke  and  G-as  Company,  of  New 
York.  For  a  coking  period  of  25  hours,  the  gas  given  off  is  divided 
as  follows :  During  the  first  10  hours  illuminating  gas  is  formed, 
it  having  a  high  illuminating  value  and  a  high  heating  value  of 
720  B.  T.  IT.  per  cubic  foot;  thereafter  fuel  gas  is  formed,  having 
a  heating  value  of  but  560  B.  T.  U.  per  cubic  foot. 

D.  BLAST  FURNACE  GAS 

The  production  of  pig  iron  is  accompanied  by  the  combustion  of 
coke.  The  gas  evolved  during  this  process  can,  after  suitable  purify- 
ing, be  used  as  a  gas  engine  fuel.  It  contains  about  5  per  cent  H, 
27  per  cent  CO,  very  small  quantities  of  CH^  and  0,  considerable 
C02  and  about  60  per  cent  N.  Hence  its  heating  value  is  very  low, 
being  about  100  B.  T.  U.  per  cubic  foot.  Its  field  of  use  is  limited 
to  iron-making  districts.  Heavy  duty  motors,  of  large  capacity,  are 
manufactured  especially  to  utilize  this  heretofore  waste  product. 
Blast  furnace  gas  requires  a  high  compression  to  facilitate  ignition 
and  combustion.  The  reason  for  this  will  appear  later. 

E.  NATURAL  GAS 

Natural  gas  is  found  in  or  near  all  oil  fields.  It  is  obviously  a 
volatile  product  of  oil  in  a  natural  state.  Many  towns  light,  heat, 
and  receive  power  from  this  source.  Its  use  as  a  gas  engine  fuel 
has  been  developed  more  rapidly  in  this  country  than  abroad.  Its 
composition  varies  with  the  well,  and  even  the  same  well  may  give 
different  results  at  different  times.  Hydrogen  and  hydrocarbons 
are  its  principal  constituents.  The  continued  supply  is  rather  un- 
certain in  any  given  district.  Excessive  II  might  cause  pre-ignition 
but,  when  not  too  high  in  H,  it  is  an  excellent  gas  engine  fuel. 
Notwithstanding  the  fact  that  it  has  a  very  high  heat  value,  it  does 
not  develop  as  much  power  as  gasoline  vapor,  which  has  a  lower 
heat  value  but  a  higher  rate  of  flame  propagation. 


14  INTERNAL  COMBUSTION  ENGINE  MANIAL 

F.  ACETYLENE 

Acetylene,  C2H2,  has  been  used  experimentally  in  internal  com- 
bustion engines.  Its  temperature  of  ignition  is  low  and  since  it 
will  ignite  spontaneously  at  low  pressures  it  is  unsuitable  for  use  in 
a  high  compression  engine.  It  has  a  high  heat  value  of  about  18,000 
B.  T.  U.  per  pound  and  having  a  high  temperature  of  combustion 
and  a  high  rate  of  flame  propagation  the  energy  derived  from  it  is 
high.  Its  cost  of  production  precludes  its  competition  with  other 
fuels  at  present.  Liquid  acetylene  has  been  suggested  as  a  possible 
fuel,  but,  as  yet,  extensive  experiments  have  not  been  conducted 
along  this  line. 


CHAPTER  II 
GENERAL 

An  internal  combustion  engine,  as  the  name  implies,  is  one  in 
which,  in  counterdistinction  to  the  steam  engine,  combustion  of 
the  fuel  takes  place  in  the  cylinder  itself.  A  steam  engine  cannot 
run  without  a  separate  unit,  the  boiler,  for  the  consumption  of  fuel 
and  generation  of  steam,  the  medium  of  motive  power.  Hence  in 
the  gas  engine  vernacular  it  is  called  an  external  combustion  engine. 
On  the  other  hand  fuel  is  fed  directly  to  the  cylinder  of  an  internal 
combustion  engine,  ignited  therein,  and  the  resulting  explosion 
acting  on  the  piston  furnishes  the  motive  power. 

The  internal  combustion  engine  is  commonly,  though  erroneously, 
called  an  explosion  engine.  The  action  which  takes  place,  and 
which  appears  to  be  an  explosion,  is  in  reality  a  progressive  com- 
bustion and  subsequent  expansion  of  the  products  of  combustion. 
Some  oil  engines  actually  carry  the  combustion  through  a  con- 
siderable part  of  the  stroke.  Although  the  expansion  line  of  an 
indicator  card  is  necessarily  of  interest  to  the  manufacturer,  the 
ratio  of  expansion  presents  no  problem,  for  the  internal  combustion 
engine  has  no  adjustable  cut-off  and  therefore  the  ratio  of  ex- 
pansion is  fixed  for  a  given  engine  by  the  clearance  space  and  the 
space  swept  by  the  piston  during  its  stroke. 

The  problem  of  expansion  is  replaced  by  questions  of  rate  of 
combustion,  rate  of  flame  propagation,  quantity  and  quality  of 
fuel,  and  most  important  of  all,  compression. 

The  question  of  compression  will  be  treated  at  length  later,  but 
a  word  here  is  necessary  to  what  follows :  when  a  fuel,  such  as  gas, 
is  admitted  to  the  cylinder  of  an  engine,  a  certain  quantity  of  air 
is  admitted  at  the  same  time  to  furnish  the  necessary  oxygen  for 
combustion.  Before  ignition  this  "  mixture''  as  it  is  called,  is 
compressed  into  a  small  space  (the  "clearance  space").  This 


16 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


compression  serves  to  mix  the  particles  of  air  and  fuel  more  inti- 
mately and  to  raise  the  temperature  of  the  mixture.  The  resultant 
compressed  mixture  will  ignite  with  more  certainty  and  will  burn 
more  evenly  than  a  rarer  and  colder  mixture. 

There  are  four  essential  systems  to  every  internal  combustion 
engine  and  these  are  treated  at  length  in  subsequent  chapters.  They 
are:  (1)  fuel  system;  (2)  ignition  system;  (3)  cooling  system;  and 
(4)  oiling  system. 

Fuel  System.  This  consists  of  a  fuel  tank  or  source  of  supply, 
a  strainer  for  liquid  fuels,  the  carbureter,  atomizer,  or  other  agent 
for  converting  the  fuel  to  a  combustible  vapor,  and  the  exhaust, 
which  usually  terminates  in  a  muffler.  In  the  case  of  liquid  fuels 


wafer  ovffef 


FIG.  3. — Schematic  Plan  of  Marine  Gasoline  Engine  Plant. 

it  is  necessary  to  volatilize  them  and  mix  with  air  before  they  can 
be  ignited  in  the  cylinder.  Fig.  3  illustrates  an  ordinary  gasoline 
fuel  system. 

Ignition  System.  If  the  ignition  is  electrical,  this  system  consists 
of  a  source  of  current  supply,  wiring,  and  a  means  of  causing  a 
spark  to  leap  a  gap,  thus  forming  an  arc  in  the  presence  of  the  fuel 
in  the  cylinder.  The  spark  thus  created  ignites  the  mixture.  If 
the  system  is  not  electrical,  then  it  consists  of  an  apparatus  de- 
signed to  bring  the  combustible  mixture  in  contact  with  a  surface 
hot  enough  to  ignite  it.  This  is  treated  in  detail  under  the  chapter 
on  ignition. 


GENERAL  17 

Cooling1  System.  This  consists  of  artificial  means  for  keeping 
the  cylinder  from  overheating  and  is  discussed  at  length  under  its 
own  heading. 

Lubrication  System.  This  is  more  complex  than  in  the  case  of 
the  steam  engine,  as  it  is  always  necessary  to  include  in  the  system 
means  of  lubricating  the  inside  of  the  cylinder.  It  is  divided  into 
internal  and  external  lubrication  as  discussed  in  a  later  chapter. 


18  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Heat  Balance.  A  table  accounting  for  the  heat  furnished  to  an 
internal  combustion  engine  is  called  the  heat  balance.  From  the 
diagram  Fig.  4,  such  a  heat  balance  might  be  constructed.  Gener- 
ally the  heat  is  accounted  for  under  four  items : 

1.  Heat  of  indicated  work. 

2.  Heat  loss  to  circulating  water. 

3.  Heat  lost  in  exhaust  gases. 

4.  Heat  of  radiation,  conduction,  etc. 

Such  a  balance  for  the  engine  under  consideration  would  be.: 

Heat  converted  into  mechanical  energy 22.7% 

Heat  lost  to  circulating  water 24.0% 

Heat  lost  in  exhaust  gases 33.3% 

Heat  lost  by  radiation,  conduction,  etc 20.0% 

~100.0% 

Items  one  and  two  can  be  determined  accurately.  The  determina- 
tion of  item  three  is  difficult  and  involves  the  weight  of  the  exhaust 
gases  and  their  specific  heats  at  the  temperature  of  the  exhaust. 
Item  four  is  the  difference  between  the  heat  supplied  and  the  sum 
of  the  other  three  items.  Sometimes  the  heat  balance  is  made  up  of 
three  parts  by  combining  items  three  and  four. 

Comparison  of  the  Internal  Combustion  Engine  and  the  Steam 
Engine.  From  the  point  of  efficiency  based  upon  the  per  cent  of 
heat  in  the  fuel  that  is  converted  into  mechanical  energy,  the  steam 
engine  shows  an  efficiency  of  from  5  per  cent  to  10  per  cent,  and  the 
internal  combustion  engine  shows  an  efficiency  of  from  17  per 
cent  to  30  per  cent.  Fig.  4  shows  the  principal  heat  losses  in  the 
two  plants. 

Although  the  engine  itself  is  in  many  cases  heavier  per  horse 
power  than  a  steam  engine,  still  the  internal  combustion  engine 
plant  is  simpler,  more  compact,  and  lighter  than  the  steam  plant 
due  to  the  absence  of  a  boiler.  Other  advantages  are : 

1.  Easier  to  start  and  stop;  warming  up  not  necessary,  and  the 
engine  is  ready  for  a  full  load  after  a  few  revolutions. 

2.  No  radiation  or  leakage  losses  in  boiler  and  piping  as  in  the 
steam  plant ;  no  "  stand  by  "  losses. 


GENERAL 


19 


Internal  Combustion  Engine  Plant. 
Diagram  of  Heat  Losses  per  Ib.  of  Fuel. 

2900 
Overall  Efficiency  lgooo— 19.3%. 


f/t*e  wor/r 
2900  G.7:i/ 


&0t. 


Steam  Engine  Plant. 
Diagram  of  Heat  Losses  per  Ib.  of  Fuel. 

1300 
Overall  Efficiency  15QOO  =  8.7%. 

FIG.  4. — Distribution  of  Heat  Energy  in  Steam  and  Internal  Combustion 

Engine  Plants. 


20  INTERNAL  COMBUSTION  ENGINE  MANUAL 

3.  Few  auxiliaries;  reduced  labor  and  attendants. 

4.  High  pressure  present  only  in  the  cylinder,  which  is  the  part 
specially  designed  to  withstand  pressure. 

The  disadvantages,  in  comparison  with  the  steam  plant,  are : 

1.  Waste  of  heat  in  the  exhaust  gases.    Up  to  date,  the  internal 
combustion  engine  has  not  been  compounded  successfully,  and  the 
utilization  of  this  exhaust  heat  is  still  an  unsolved  problem. 

2.  Whereas  the  steam  engine  cylinder  is  kept  at  as  high  a  tem- 
perature as  possible  to  prevent  liquefaction,  this  does  not  hold  in  an 
internal  combustion  engine.     A  large  amount  of  heat  must  be 
absorbed  by  the  cooling  water  to  prevent  overheating  and  injury 
to  the  cylinder.    It  is  found  that,  roughly  speaking,  the  maximum 
efficiency  is  obtained  if  the  circulating  water  is  kept  as  near  the 
boiling  point  as  possible. 

3.  The  internal  combustion  engine  is  not  as  uniform  in  its  im- 
pulse and  speed  as  the  steam  engine  and  until  recent  years  has  not 
been  considered  as  reliable.    This  has  been  due  in  part  to  ignorance 
on  the  part  of  operators,  and  it  is  safe  to  assume  that  a  good  internal 
combustion  engine  per  se  is  as  reliable  as  a  steam  engine.    Eecent 
developments  in  governing  have  given  such  a  uniform  speed  that 
alternating  current  generators  in  parallel  are  driven  by  some  of  the 
gas  engines  on  the  market. 

The  ideal  condition  of  an  impulse  per  stroke,  which  is  present  in 
the  steam  engine,  is  not  attained  in  the  internal  combustion  engine 
except  in  one  case,  that  of  the  double  acting  tandem  engine  which 
cannot  be  used  for  all  kinds  of  work.  Only  one  impulse  is  received 
for  each  two  or  four  strokes  in  a  single  cylinder  engine,  and  the 
engine  must  be  multicylinder  to  get  a  continuous  impulse.  Six 
cylinders  is  the  least  that  will  furnish  an  overlapping  impulse  if 
the  engine  be  four  cycle. 

The  rapid  strides  in  the  development  of  the  internal  combustion 
engine  are  due  quite  as  much  to  the  demands  of  the  sporting  as  of 
the  industrial  world.  The  automobile  industry  has  developed  the 
high-speed  motor  to  such  a  point  that  there  is  little  improvement  in 
sight.  The  aeroplane  was  made  possible  by  the  gasoline  engine.  All 
the  other  problems  of  human  flight  were  solved  years  before  suitable 


GENERAL  21 

motive  power  was  available.  On  the  other  hand,  the  industrial  world 
was  not  behind  in  developing  the  slow-speed,  heavy-duty  motor,  and 
we  now  find  internal  combustion  engines  employed  for  every  con- 
ceivable duty  from  aeroplane  propulsion  to  furnishing  the  motive 
power  for  agricultural  machinery. 

For  marine  use,  gasoline  and  oil  engines  have  shown  their  effi- 
ciency in  small  units,  such  as  launches,  torpedo-boats,  etc.,  and 
recently  internal  combustion  engine  installation  on  ships  as  large 
as  8000  tons  seem  to  have  been  attended  with  success.  Eecently 
much  foreign  discussion  has  been  raised  about  installing  a  plant  as 
main  engines  on  a  first-class  cruiser  or  battleship,  but  no  reliable 
information  in  support  of  this  can  be  obtained.  It  is  possible  that 
some  foreign  government  will  install  a  17,000  horse-power  plant  of 
the  Diesel  type. 

From  the  foregoing  balance  of  advantages  in  favor  of  the  internal 
combustion  engine,  and  from  its  remarkable  overall  efficiency  it 
must  not  be  concluded  that  this  type  engine  will  ultimately  sup- 
plant the  steam  engine  and  turbine.  In  a  coking  region  or  blast 
furnace  plant,  where  a  fuel  supply  is  obtained  from  an  otherwise 
waste  product,  there  can  be  no  question  of  its  supremacy,  but  for 
marine  use  there  are  several  inherent  difficulties  to  overcome. 

Probably  the  most  important  of  these  is  the  fact  that  an  oil 
engine  run  continuously  for  more  than  twelve  hours  is  subject  to 
deterioration  due  to  metallic  disintegration  of  cylinder  walls  from 
severe  vibration  in  the  presence  of  intense  heat.  Since  the  oil  en- 
gine is  the  logical  type  for  marine  use  it  would  appear  that  there 
are  still  unsolved  problems  to  be  dealt  with,  and  experiments  now 
underway  may  produce  wonderful  results  in  the  near  future. 

As  early  as  1862  Beau  de  Eochas  announced  the  four  requisites 
for  economical  and  efficient  working  of  internal  combustion  engines, 
and,  with  one  exception,  these  are  undisputed  to-day.  They  are : 

1.  The  greatest  possible  cylinder  volume  with  the  least  possible 
cooling  surface. 

2.  The   greatest  possible  rapidity   of   expansion.      Hence,   high 
speed. 

3.  The  greatest  possible  expansion.     Hence,  long  stroke. 


22  INTERNAL  COMBUSTION  ENGINE  MANUAL 

4.  The  greatest  possible  pressure  at  the  beginning  of  expansion. 
Hence,  high  compression. 

Of  course  the  type  of  motor  must  depend  upon  the  particular 
work  it  is  intended  to  perform.  Much  discussion  has  arisen  on  the 
merits  of  the  long  or  short  stroke  motor.  The  long  stroke  gives 
a  greater  expansion,  but  it  also  increases  the  duration  of  contact  of 
the  gases  with  the  cylinder  walls,  hence  increasing  the  radiation 
losses,  etc.  The  short  stroke  decreases  the  expansion,  but  it  also 
decreases  the  radiation  losses.  This  point  must  be  settled  by  other 
considerations  arising  from  the  particular  duty  that  the  motor  will 
perform. 


CHAPTER  III 
CONSTRUCTION 

The  subject  of  internal  combustion  engine  construction  will  have 
to  be  treated  in  a  very  general  manner  because  of  the  variety  of 
forms  of  all  the  parts  found  in  different  types.  Naturally  the 
design  of  engine  depends  upon  the  service  it  is  intended  to  perform, 
thus,  the  aeroplane  engine  has  been  constructed  to  weigh  as  little 
as  two  pounds  per  horse-power,  whereas  engines  for  marine  use 


FIG.  5. — Water  Cooled,  Four 
Cycle  Cylinder. 


FIG.  6. — Air  Cooled,  Four 
Cycle  Cylinder. 


weight  from  45  to  60  pounds  per  horse-power.  With  the  many  types 
existing  it  is  only  possible  to  give  a  few  general  forms  of  parts. 

Cylinder.  Cylinders  may  be  cast  singly  or  en  bloc,  that  is,  in  a 
multicylinder  engine  each  cylinder  may  be  cast  as  a  separate  unit 
or  two  or  more  may  be  cast  in  one  piece.  They  are  generally  classi- 
fied as  (1)  water  cooled  and  (2)  air  cooled,  depending  upon  the 
system  adopted  to  prevent  overheating  of  the  cylinder.  Fig.  5 


INTJ:RXAL  COMBUSTION  ENC;  i  x  i:   M  AN  LA  L 


shows  a  water  cooled  cylinder  with  the  annular  space  in  which  to 
circulate  water.  Fig.  6  shows  an  air  cooled  cylinder.  The  ribs  east 
on  the  outside  of  this  cylinder  increase  the  radiating  surface  of 
the  cylinder  and  thus  serve  the  same  purpose  as  the  circulating 
water  in  the  other  type.  It  should  be  noted  that  the  annular  space 
and  the  ribs  do  not  extend  the  full  length  of  the  cylinder,  but  only 
cover  the  upper  part.  They  only  extend  a  little  below  the  com- 
pression space  which  is  the  hottest  part  of  the  cylinder  as  will 
appear  later.  Fig.  7  shows  a  water  cooled  cylinder  Avith  a  copper 


FIG.  7. — Copper  Jack- 
eted Cylinder. 


Fro.  8.— Pair  of  Cylinders  Cast 
en  bloc. 


water  jacket  fastened  and  caulked  to  the  cylinder.  The  corruga- 
tions shown  allow  for  the  unequal  expansion  of  the  copper  of  the 
jacket,  and  the  iron  of  which  the  cylinder  is  cast.  This  con- 
struction is  the  more  expensive  of  the  two  and  is  only  used  in  auto- 
mobile and  aeroplane  engines.  Fig.  8  illustrates  a  pair  of  cylinders 
cast  en  bloc. 

Cylinders  are  made  of  close  grain,  gray,  cast  iron,  hardness  being 
the  essential  requisite.  The  previous  four  illustrations  portray 
the  four  cycle  type  engine;  Fig.  9  shows  the  general  type  two  cycle 
cylinder  without  valves;  the  piston  passing  over  the  port  openings 
acts  as  a  valve.  The  cvlinders  are  counterbored  at  the  end  of  the 


CONSTRUCTION  25 

stroke.  This  prevents  the  formation  by  the  ring  of  a  collar  at  each 
end  of  its  travel. 

Piston.  The  majority  of  internal  combustion  engines  are  single 
acting,  receiving  the  impulse  on  only  one  end  of  the  piston.  The 
impulse  is  much  more  sudden  than  in  the  case  of  the  steam  engine, 
and  if  the  piston  were  constructed  disc  shaped,  as  in  the  steam 
engine,  there  would  be  a  tendency  to  cant  or  dish  on  the  explosion 
stroke.  For  this  reason  and  for  the  purpose  of  aiding  packing,  cool- 
ing and  guiding  generally,  the  piston  is  made  long  and  hollow,  the 


Wafer 

FIG.  9. — Two  Cycle  Water  Cooled  Cylinder. 

length  for  a  good  four  cycle,  high-speed  design  being  about  one  and 
one-half  times  the  diameter.  In  this  type  the  length  precludes  the 
necessity  for  connecting  rod  and  guides.  The  piston  tapers,  the 
explosion  end  being  slightly  smaller,  say  .001  of  the  diameter,  than 
the  opposite  end.  The  reason  for  this  is  that  the  explosion  end, 
being  in  contact  with  the  hot  gases,  when  running,  will  expand 
more  than  the  other  end.  It  is  fitted  with  eccentric  rings,  usually 
four,  which  spring  into  grooves  shown  in  Fig.  10,  the  lowest  ring 
acting  as  an  oil  ring.  Fig.  11  shows  a  piston  with  rings,  connect- 
ing rod  and  bearings,  all  assembled.  Heavy  duty  and  double  acting 
engines  have  different  types  of  pistons,  some  being  of  such  a  form  as 
to  require  piston  rod,  connecting  rod  mid  guides.  These  are  illus- 
trated in  Chapter  X. 


26 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


FIG.  10. — Piston,  Showing  Method  of  Securing 
Connecting  Rod. 

Figs.  12  and  13  are  two  types  of  piston  heads  for  two  cycle  en- 
gines. The  dished  head,  Fig.  12,  and  the  web  cast  on  top  of  the 
piston,  Fig.  13,  serve  to  deflect  the  incoming  gases  and  thus  aid  in 
scavenging  the  cylinder. 


FIG.  11. — Piston  with  Rings,  Connecting  Rod 
and  Bearings  Assembled. 


CONSTRUCTION 


Connecting  Rod  and  Wrist  Pin.  In  all  engines,  except  the 
large  stationary  ones,  the  piston  rod  is  absent,  the  piston  motion 
being  communicated  to  the  crank  direct  by  the  "  connecting  rod." 
At  the  piston  end  the  rod  is  connected  to  the  "  wrist  pin."  There 
are  two  ways  of  forming  this  bearing;  first — the  one  most  com- 
monly used — the  wrist  pin  is  locked  fast  to  the  piston,  the  rod 
working  on  it;  and  second,  the  rod  is  locked  fast  to  the  wrist  pin 
and  the  pin  works  in  the  piston  as  a  bearing.  Pig.  10  illustrates  the 


FIG.  12.  FIG.  13. 

Two  Cycle  Piston  Heads. 

first  method,  a  set  screw  and  lock  nut  being  shown  in  place.  Eods 
are  forged  or  drop  forged  steel,  the  heavy  stationary  engines  having 
rods  of  rectangular  section  and  the  marine  and  lighter  engines 
having  an  "  I  "  section  rod. 

Valves.  The  most  common  and  best  developed  valve  at  present 
is  the  disc,  poppet  valve  shown  in  Fig.  14.  Drop  forged  valves 
answer  the  purpose  for  all  but  the  heavier  engines  which  require 
valves  cast  in  one  piece.  The  best  material  must  be  used  in  valves, 
especially  the  exhaust,  as  they  are  subject  to  the  intense  heat  of  ex- 
plosion, and  the  exhaust  valves  receive  the  full  corrosive  effect  of 
the  fast  moving,  hot  exhaust.  The  smaller  valves  have  a  slot  in 
the  head  to  fit  a  screw-driver  or  tool  for  regrinding  to  the  seat. 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


The  requirements  for  an  efficient  valve  are:  (1)  it  must  be  gas 
tight  without  excessive  friction;  (2)  the  opening  and  closure  must 
be  instantaneous;  (3)  it  must  be  accessible  for  cleaning,  grinding, 
etc. ;  (4)  the  gases  must  not  be  wire  drawn.  The  exhaust  valve  is 
generally  actuated  by  cam  gear  situated  on  a  countershaft  that  is 
geared  to  the  main  shaft.  This  is  also  the  better  method  for  act- 
uating the  admission  valve,  although  some  engines  are  fitted  with 
spring  loaded  admission  valves  that  lift  automatically  on  the  suc- 
tion stroke.  In  some  designs  a  rod  and  rocking  lever,  actuated  by 
a  cam,  opens  alternately  both  admission  and  exhaust  valves  of  the 
same  cylinder.  The  Curtis  engine  and  many  motorcycle  engines  are 
of  this  type. 


FIG.  14. — Conical  Disc,  Poppet  Valve. 

There  are  a  variety  of  novel  valves,  such  as  rotating  valves,  that 
have  not  received  general  recognition.  The  Knight  motor  has  two 
reciprocating  sleeves  between  the  piston  and  the  cylinder.  These 
sleeves  contain  openings  that  cover  and  uncover  the  port  openings 
at  the  proper  points  of  the  cycle  and  thus  act  alternately  as  ad- 
mission and  exhaust  valve.  The  larger  exhaust  valves  are  hollow 
to  permit  circulation  of  water  for  cooling  the  valve. 

Push  Hods.  Interposed  between  the  valve  stem  and  the  cam  on 
the  countershaft  is  a  push  rod,  Fig.  15.  As  seen  in  Fig.  20  these 
are  carried  in  guides  that  fasten  to  the  engine  base.  On  the  lower 
end  is  a  hard  steel  roller  that  bears  on  the  cam  giving  a  minimum 
friction.  In  the  latest  practice  for  high  speed  engines  the  top  of 
the  push  rod  has  an  adjustable  screw  that  bears  on  the  valve  stem  so 
that  wear  on  the  end  of  the  rod  can  be  compensated;  this  tends  to- 
ward quiet  running,  and  aids  valve  timing. 


CONSTRUCTION  29 

Fly- Wheel.  On  account  of  the  intermittent  impulse  given  an 
internal  combustion  engine  shaft,  all  engines  having  six  or  less 
•ir  or  king  cylinders  require  a  fly-wheel.  By  its  inertia  it  tends  to  give' 
a  uniform  rotation  to  the  shaft  in  spite  of  the  non-uniform  crank 
effort.  Obviously,  the  relative  size  of  fly-wheel  required  increases 
with  the  decrease  in  the  number  of  working  cylinders.  The  same 
features  govern  fly-wheel  design  whether  for  internal  combustion 
or  other  engines,  except  that  more  care  must  be  taken  in  the  balance 
of  those  used  in  this  particular  field. 


V 

Va/ve 
Sfesr? 


Rod* 


Counter  5/H7/J 


FIG.  15.  —  Push  Rod. 


Balancing  the  Crank  Arm.  Single-throw  cranks  for  high-speed 
engines  are  provided  with  balance  weights  to  balance  the  weight 
of  the  crank  pin,  web,  and  that  part  of  the  connecting  rod  that  is 
regarded  as  rotative.  These  weights  are  generally  located  on  both 
crank  webs,  and  must  be  securely  fastened,  because  any  play  be- 
tween them  and  the  web  would  rapidly  increase  from  the  engine 
vibration  and  would  cause  serious  trouble. 

Muffler.  For  quiet  operation  the  muffler  is  an  essential  part  of 
the  exhaust  system.  Exhausting  into  the  atmosphere  at  the  normal 
exhaust  pressure  causes  a  sharp  disagreeable  noise.  This  is  so 
annoying  that  many  municipalities  have  passed  ordinances  requir- 
ing that  all  internal  combustion  engines  be  fitted  with  mufflers. 

A  muffler  is  merely  an  enlargement  near  the  end  of  the  exhaust 
line  to  allow  a  gradual  expansion  of  the  exhaust  gases  to  the  at- 


30 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


mospheric  pressure.  Though  there  are  a  variety  of  forms,  the 
principle  is  the  same  in  all.  Cast  iron  is  generally  used  in  con- 
struction as  this  best  resists  the  corrosive  effects  of  the  hot  gases. 
Some  mufflers  are  fitted  with  baffles,  and  in  this  case  care  must 
be  taken  in  the  design  to  prevent  a  back  pressure  in  the  exhaust. 
A  properly  designed  muffler  will  reduce  the  pressure  at  the  muffler 
exit  without  reducing  the  speed  of  the  exhaust  from  the  engine  to 
the  muffler.  As  long  as  this  speed  is  maintained  110  back  pressure 
will  result.  In  stationary  plants  water  spray  is  sometimes  injected 


FIG.  16. — Thompson  Muffler. 

into  the  muffler  to  condense  the  gases.  This  is  a  common  marine 
practice. 

The  Thompson  Muffler,  Fig.  16,  best  illustrates  the  muffler  prin- 
ciple. This  consists  of  a  cylindrical  chamber  with  a  hooded  inlet 
pipe  of  increasing  volume.  The  exhaust  puffs  pass  into  a  large 
chamber  where  they  expand  and  pass  out  of  the  exit  pipe  in  a  steady 
stream  of  practically  constant  pressure. 

The  gas  pipe  muffler,  Fig.  17,  operates  on  the  same  principle  as 
the  Thompson,  but  is  of  a  cruder  design. 

The  ejector  muffler,  Fig.  18,  is  designed  as  its  name  implies,  on 
the  principle  of  an  ejector.  It  consists  of  three  expansion  chambers 


CONSTRUCTION 


31 


which  are  formed  by  conical  baffle  plates,  perforated  top  and  bottom, 
arranged  in  two  sets.  The  axial  tube,  leading  through  the  muffler, 
is  of  varying  diameter  and  a  part  of  the  gas  entering  the  muffler 
passes  directly  into  the  center  chamber  and  through  the  second  set 
of  cones  before  the  gas  which  has  entered  the  first  chamber  has 


-T7T 


oooo°ooo 

ooooooooo0o0ooo0o 


a  Es*a  fe^d  te^  fe^i  k 


PIG.  17.— Gas  Pipe  Muffler. 

passed  through  the  first  set.  A  portion  of  the  gas  is  conducted 
straight  through  the  center  pipe  to  the  nozzle  at  a  high  velocity 
which  creates  a  partial  vacuum  in  the  third  chamber.  The  rapid 
forward  movement  of  the  gas  through  the  first  and  second  chambers 
to  the  third,  causes  a  sudden  expansion,  removing  the  heat  from 


PIG.  18. — Ejector  Muffler. 


the  gas  and  reducing  the  pressure  in  the  muffler  to  below  that  of  the 
atmosphere.  This  allows  the  gas  to  escape  without  noise  and  with- 
out back  pressure.  Water  mayvbe  used  in  this  type,  and  it  is  very 
suitable  for  marine  use. 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


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CONSTRUCTION 


33 


Underwater  Exhaust.  Fig.  19  illustrates  a  common  form  of 
exhaust  below  the  water  line.  In  this  case  there  are  two  outlets 
from  the  muffler.  This  form  is  a  little  more  expensive  than  that 
with  one  outlet,  but  it  is  used  considerably  with  the  ejector  muffler. 


FIG.  19. — Underwater  Exhaust. 

Countershaft  for  Multicylinder  Engine.  In  a  multicylinder 
engine  where  there  are  numerous  valves,  etc.,  to  be  actuated  by 
cams,  a  countershaft,  sometimes  called  the  cam  shaft,  is  fitted. 
This  is  a  small  shaft,  running  the  length  of  the  engine,  parallel  to 
and  geared  to  the  engine  main  shaft.  In  addition  to  actuating  all 
the  valves  this  shaft  sometimes  actuates  the  timer,  pumps,  etc.  It 
is  geared  to  the  main  shaft  of  a  four  cycle  engine  in  the  ratio  of 
one  to  two  because  each  operation  at  any  one  valve  must  take  place 
every  second  revolution.  Fig.  20  shows  the  countershaft  as  oper- 
ating in  a  marine  or  other  high  speed  engine.  It  is  made  of  the 
best  nickel  steel.  Engines  designed  with  admission  and  exhaust 
valves  on  opposite  sides  of  the  cylinders  require  two  countershafts. 


CHAPTEE  IV 
TYPES,  CYCLES,  ETC. 

Cycles 

"A  cycle  in  engineering  is  any  operation  or  sequence  of  opera- 
tions that  leaves  the  conditions  the  same  at  the  end  that  they  were 
in  the  beginning."  An  internal  combustion  engine  cycle  consists 
of:  (1)  suction  or  admission  of  the  charge;  (2)  compression;  (3) 
ignition,  combustion  and  expansion;  (4)  exhaust.  The  number  of 
strokes  necessary  to  complete  this  cycle  gives  a  means  of  cyclic  classi- 
fication as  follows:  (1)  two-stroke  cycle;  (2)  four-stroke  cycle. 
The  common  terms  for  these  are  two  cycle  and  four  cycle.  The 
latter  is  sometimes  called  the  Beau  de  Koch  a  cycle,  or  more  com- 
monly the  Otto  cycle.  The  two  cycle  is  sometimes  called  the  Clerk 
cycle. 

Four  Cycle 

Figs.  21  to  24,  inclusive,  illustrate  the  four  strokes  forming  a 
complete  cycle  in  a  four  cycle  engine.  The  piston  is  shown  near 
the  finish  of  the  stroke  in  each  case. 

Admission.  In  Fig.  21  the  piston  has  traveled  one  down  stroke. 
During  this  stroke  the  admission  valve  is  open  and  the  vacuum 
formed  by  the  down  stroke  of  the  piston  has  been  filled  by  the  in- 
rush of  a  fresh  charge  of  combustible  mixture.  This  is  called  the 
suction  or  aspiration  stroke.  The  admission  valve  closes  at  the  end 
of  this  stroke. 

Compression,  Fig.  22.  During  this  up  stroke  both  valves  are 
closed  and  the  charge  is  compressed  into  a  small  space  at  the  cylin- 
der end  called  the  "  clearance  space."  The  necessity  for  compres- 
sion will  be  shown  later. 


TYPES,  CYCLES,  ETC. 


35 


Ignition,  Fig.  23.  This  third  stroke  is  the  power  stroke  and  is 
variously  known  as  the  ignition,  combustion,  expansion,  or  ex- 
plosion stroke.  During  this  stroke  both  valves  are  closed.  At  the 
beginning  of  the  stroke  the  charge  is  ignited  and  the  subsequent 
expansion  furnishes  the  motive  impulse  to  the  piston,  driving  it  to 
the  end  of  its  stroke. 


FIG.  21.  FIG.  22.  FIG.  23.  FIG.  24. 

Periods  in  the  Cycle  of  a  Four  Cycle  Engine. 

Exhaust,  Fig.  24.  The  exhaust  valve  opens  at  or  near  the  end 
of  the  expansion  stroke  and  the  up  travel  of  the  piston  on  this 
fourth  stroke  forces  the  gases  of  combustion  out  of  the  cylinder 
completing  the  cycle. 

As  the  engine  receives  only  one  impulse  every  fourth  stroke  means 
must  be  employed  to  drive  the  engine  throughout  the  remaining 
three.  A  fly-wheel,  which  accomplishes  this  by  its  inertia,  is  in- 
stalled on  the  main  shaft.  In  the  case  of  multicylinder  engines  the 
fly-wheel  by  its  inertia  balances  the  impulses  and  gives  a  steady 
speed. 


36 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


Two  Cycle 

The  two  cycle  engine  requires  only  two  strokes  or  one  revolution 
to  complete  the  cycle.  As  seen  from  Fig.  25,  the  crank  case  is 
closed  gas  tight  and  a  spring  loaded  admission  valve  opens  to  the 
crank  case.  Instead  of  the  admission  and  exhaust  being  regulated 
by  valves,  port  openings  in  the  cylinder  sides  are  uncovered  by  the 


FIG.  25.  FIG.  26. 

Periods  in  the  Cycle  of  a  Two  Cycle  Engine. 

piston  at  proper  points  in  the  stroke  and  these  openings  communi- 
cate with  the  fuel  supply  and  the  exhaust  passage.  The  piston 
functions  as  valves.  The  port  a,  Fig.  25,  connects  the  crank  case 
and  cylinder  around  the  piston,  when  at  the  bottom  of  its  stroke. 
Deflecting  plate  b  aids  in  scavenging  the  cylinder. 

Two  circles  in  the  crank  case,  Fig.  25,  illustrate  the  steps  in 
the  cycle.  The  inner  circle  indicates  operations  in  the  crank  case 
and  the  outer  circle  indicates  simultaneous  periods  in  the  cycle  on 


TYPES,  CYCLES,  ETC.  37 

top  of  the  piston.  Starting  from  the  position  shown  in  Fig.  25,  the 
charge  is  compressed  in  the  top  of  the  cylinder  and  has  just  been 
ignited.  The  crank  case  is  full  of  a  fresh  charge  that  has  just  been 
drawn  through  the  admission  valve.  The  piston  is  driven  down 
by  the  expansion.  The  port  d  being  covered,  the  charge  in  the 
crank  case  is  compressed  on  the  down  stroke.  Expansion  takes 
place  in  the  cylinder  to  the  point  1  and  when  this  point  is  reached 
by  the  crank,  the  exhaust  port  is  uncovered  relieving  the  pressure. 
At  the  point  2,  port  d  is  opened  allowing  communication  between 
the  crank  case  and  the  cylinder.  The  compressed  charge  in  the 
crank  case  rushes  into  the  cylinder  displacing  the  exhaust  gases 
which  escape  through  the  exhaust  port  e,  Fig.  26.  On  the  return 
stroke  when  the  point  3  is  reached  port  d  is  covered  by  the  piston 
and  the  up  travel  of  the  piston  creates  a  vacuum  in  the  crank  case, 
opens  the  admission  valve  and  sucks  a  fresh  charge  into  the  crank 
case.  At  the  point  4  the  exhaust  port  is  covered  and  from  this 
point  to  point  5  the  fresh  charge  on  top  of  the  piston  is  compressed. 
At  point  5  ignition  takes  place  completing  the  cycle.  At  (5  the 
spring  loaded  admission  valve  to  the  crank  chamber  closes. 

As  the  piston  receives  an  impulse  every  other  stroke,  a  fly-wheel 
is  employed  to  drive  the  piston  through  the  non-impulse  stroke. 
The  two  cycle  engine  is  sometimes  called  a  valveless  engine  on 
account  of  the  absence  of  valves. 

Advantages  and  Disadvantages  of  the  Two  Cycles. 

Two  Cycle.  Advantages.  N"o  valves,  valve  gear,  cams  and  cam 
shaft;  more  uniform  turning  moment  and  lighter  fly-wheel;  smaller 
cylinder  volume  per  unit  of  power;  simplicity  and  compactness. 

Disadvantages.  Loss  of  fresh  fuel  with  exhaust  reduces  the 
economy;  crank  case  must  be  kept  gas  tight  to  prevent  loss  of  fuel 
and  compression;  fresh  fuel  entering  the  cylinder  full  of  hot  ex- 
haust gases  may  cause  premature  explosion,  and  if  this  occurs 
before  the  admission  port  is  closed,  the  crank  case  charge  may  ex- 
plode, causing  considerable  damage  to  the  engine.  For  large 
engines  an  auxiliary  pump  is  employed  to  replace  crank  case  com- 
pression. 
4 


38  INTERNAL  COMBUSTION  ENGINE  MANUAL 

/ 

Four  Cycle.  Advantages.  Better  explosion  control;  more  eco- 
nomical; compression  not  dependent  upon  tightness  of  any  part 
except  valves  and  piston  rings;  no  auxiliary  pump  required;  gas 
tightness  of  crank  case  immaterial. 

Disadvantages.  Cylinder  volume  arid  weight  per  unit  of  power 
greater;  multiplicity  of  parts,  especially  valves,  valve  gear,  cams, 
countershaft,  etc.,  with  increased  probability  of  breakdown :  loss  of 
power  if  any  valves  are  not  gas  tight. 

The  four  c^ycle  engine  seems  to  lose  in  simplicity  by  comparison 
with  the  two  cycle,  but  it  is  in  far  more  common  use. 

Although  the  two  cycle  engine  receives  twice  as  many  impulses 
per  revolution  as  the  four  cycle,  it  must  not  be  concluded  from 
this  that,  for  the  same  cylinder  dimensions,  the  two  cycle  has  twice 
the  power.  In  the  four  cycle  type  the  impulse,  due  to  expansion, 
is  carried  throughout  nearly  the  entire  stroke,  whereas,  in  the  two 
cycle  type,  the  exhaust  valve  opens  much  earlier  and  the  impulse 
only  lasts  about  five-eighths  'of  the  stroke,  as  can  be  seen  from  Fig. 
25. 

Types 

The  internal  combustion  engine  is  commonly  called  by  a  variety 
of  names,  none  of  which  are  technically  correct  for  all  types,  for 
example,  gas  engines,  explosion  engines,,  lieat  engines,  etc.  Two 
general  subdivisions  may  be  made,  viz.:  (1)  single  acting;  (2) 
double  acting. 

A  single  acting  engine  is  one  which  receives  the  motive  impulse 
on  only  one  side  of  the  piston. 

A  double  acting  engine  is  one  which  receives  the  motive  impulse 
alternately  on  both  sides  of  the  piston. 

All  of  the  small  high-speed  engines  are  single  acting,  and,  with  a 
few  exceptions,  only  the  large,  low-speed,  heavy-duty  motors  are 
made  double  acting. 

A  very  common  and  unscientific  method  of  classifying  internal 
combustion  engines  depends  upon  the  fuel  consumed,  thus,  gas 
engine,  gasoline  engine,  oil  engine,  alcohol  engine,  alco  vapor  engine, 
etc.  This  a  common  commercial  practice. 


TYPES,  CYCLES,  ETC.  39 

The  only  scientific  classification  is  a  thermodynamic  one.  Heat 
is  imparted  to  the  fuel  and  medium  by  the  chemical  reaction  that 
follows  ignition.  The  method  of  applying  this  heat  to  the  working 
substance  determines  the  class  in  which  the  engine  belongs.  The 
classification  is  as  follows: 

1.  Engines  receive  heat,  the  charge  being  at  constant  volume. 

2.  Engines  receive  heat,  the  charge  being  at  constant  pressure. 

3.  Engines  receive  heat,  the  charge  being  at  constant  temperature. 

Ignition  with  Charge  at  Constant  Volume 

This  class  of  engine  is  the  one  in  most  common  use  and  is  fre- 
quently erroneously  called  an  explosion  engine.  The  whole  charge, 
which  is  drawn  in  on  the  aspiration  stroke  and  compressed,  is  ig- 
nited, and,  the  charge  occupying  a  small  space,  the  rate  of  flame 
propagation  is  so  rapid  that  the  charge  practically  burns  without 
change  of  volume  before  expansion  takes  place.  In  other  words 
combustion  is  complete  before  expansion  starts.  The  subsequent 
rapid  expansion,  with  its  accompanying  rise  of  pressure,  furnishes 
the  motive  powrer.  All  engines  using  gas  or  carbureted  fuel  ignite 
at  constant  volume. 

Ignition  with  Charge  at  Constant  Pressure 

This  principle  was  adopted  by  Brayton  in  his  engine  about  1870. 
He  apparently  got  his  idea  from  the  action  of  the  steam  engine  to 
which  its  cycle  is  analogous.  Separate  pumps  supplied  air  and 
combustible  to  the  cylinder  at  constant  pressure  and  the  mixture 
burned  as  it  entered.  The  pressure  was  therefore  constant  during 
the  expansion  or  combustion  stroke  until  the  admission  valve  closed. 
The  increased  volume  at  constant  pressure  drove  the  piston.  This 
engine,  which  was  at  one  time  popular  in  this  country,  is  no  longer 
manufactured.  The  latest  Diesel  engine  manufactured  in  Germany 
approaches  this  principle. 

Ignition  with  Charge  at  Constant  Temperature 

The  card  from  an  engine  built  on  this  principle  would  have  a 
combustion  line  which,  when  analyzed,  would  prove  to  be  isothermal. 


40  INTERNAL  COMBUSTION  ENGINE 

As  late  as  1904  the  American  Diesel  Engine  Company  claimed  this 
for  their  engine.  This  is  rather  surprising  in  view  of  the  fact  that 
isothermal  combustion  is  theoretically  the  least  efficient.  It  would 
be  possible  to  construct  an  engine  of  the  Diesel  cycle  whereby,  air 
being  previously  compressed  in  the  cylinder  to  a  very  high  tem- 
perature, the  fuel  could  be  injected  during  the  combustion  stroke  at 
such  a  rate  as  to  maintain  this  temperature.  This  presupposes  a 
very  accurate  and  minute  fuel  supply  regulation. 

It  can  be  shown  mathematically  that  combustion  at  constant 
volume  gives  the  most  efficient  cycle  and  that  combustion  at  con- 
stant temperature  gives  the  least  efficient.  Combustion  at  constant 
pressure  gives  a  cycle  which  is  between  these  two  in  efficiency. 

Compression 

Compression,  which  immediately  precedes  ignition,  is  one  of  the 
greatest  factors  in  internal  combustion  engine  efficiency.  With  a 
given  amount  of  fuel  to  be  burned,  if  this  fuel  were  not  compressed, 
the  cylinder  volume  would  necessarily  be  increased  by  the  ratio  of 
expansion  and  would  be  enormous  were  the  engine  non-compression. 
This  was  recognized  by  the  inventors  of  the  first  efficient  gas  engine 
as  the  underlying  principle  of  success.  Thus  it  is  apparent  that 
compression  is  absolutely  necessary. 

By  compressing  the  mixture  into  a  small  space  the  atoms  of  the 
fuel  are  more  intimately  mixed,  thus  aiding  combustion,  and  they 
are  brought  more  closely  together  thus  accelerating  flame  propaga- 
tion. Compression  heats  the  mixture,  thus  aiding  ignition  and 
increasing  the  initial  temperature ;  it  also  greatly  increases  the 
mixture's  power  of  expansion. 

By  increasing  the  compression  the  necessary  clearance  or  com- 
pression space  is  reduced;  this  reduces  the  cylinder  wall  area  of 
radiation  and  water  jacket  length  and  as  a  direct  result  the  loss  of 
heat  by  radiation  is  diminished.  Reducing  the  clearance  space  is  the 
equivalent  of  increasing  the  stroke.  If  the  compression  is  too  low 
the  fuel  may  not  all  burn,  due  to  poor  flame  propagation,  and  some 
gases  will  not  ignite  at  all  unless  compressed  to  a  certain  pressure. 

There  is  a  practical  limit  to  the  degree  of  compression  that  may 


TYPES,  CYCLES,  ETC.  41 

be  attained.  This  depends  upon  the  ignition  temperature  of  the 
fuel.  As  stated  above,  compression  increases  the  temperature  and, 
if  this  is  carried  too  far,  premature  ignition  will  result.  The  fol- 
lowing limits  in  pounds  are  given  by  Lucke :  Carbureted  gasoline, 
high-speed  engine,  45-95;  carbureted  gasoline,  slow-speed,  well- 
cooled  engine,  60-85;  kerosene,  hot  bulb  injection  and  ignition,  30- 
75;  kerosene,  vaporized,  45-85;  natural  gas,  75-130;  producer  gas, 
100-160;  blast  furnace  gas,  120-190.  The  degree  of  compression 
that  is  necessary  for  efficiency  depends  upon  the  ignition  point  of 
the  fuel,  increasing  with  this  temperature. 


CHAPTEE  V 

CARBURETION,  THE  MIXTURE,  ITS  PREPARATION, 
CARBURETERS  AND  VAPORIZERS 

Definitions 

Carburetion  is  the  process  of  saturating  air  or  gas  with  a  hydro- 
carbon. 

The  air  or  gas  that  is  carbureted  is  called  the  medium. 

The  carburizer  is  the  agent  (fuel)  employed  to  saturate  the  air. 

A  carbureter  is  an  apparatus  used  to  charge  air  or  gas  with  a 
volatilized  hydrocarbon. 

"  The  mixture "  is  the  term  commonly  employed  in  the  gas 
engine  world  to  designate  the  product  of  the  carbureter  when  ready 
for  combustion,,  viz. :  the  combination  of  fuel  and  air. 

A  "  rich  "  mixture  is  one  having  an  excess  of  fuel,  and  a  "  lean  " 
mixture  is  one  having  an  excess  of  air. 

A  ee  charge  "  is  a  cylinder  full  of  mixture. 

Every  fuel  requires  a  certain  amount  of  oxygen  for  complete 
oxidation  or  combustion.  This  can  be  supplied  by  the  atmosphere 
if  suitable  means  are  at  hand  to  mix  the  air  and  fuel.  The  various 
fuels  contain  different  proportions  of  carbon,  hydrogen  and  other 
combustibles,  therefore,  will  require  proportionate  amounts  of  air 
to  attain  complete  combustion.  Excessive  air  will  cool  the  mixture, 
greatly  reduce  the  rate  of  flame  propagation,  and  weaken  the  ig- 
nition if  it  does  not  actually  prevent  it.  Its  increased  volume 
causes  increased  loss  of  heat  in  the  exhaust  gases.  Too  little  air 
will  result  in  incomplete  combustion,  reducing  the  efficiency  and 
causing  a  carbon  deposit  in  the  cylinders,  etc. 

The  function  of  a  carbureter  or  of  a  mixing  valve  is  to  admix 
the  fuel  and  air  to  the  correct  richness,  forming  a  combustible  gas 
or  vapor.  The  rapid  advance  in  the  development  of  the  modern 
internal  combustion  engine  is  due  in  large  part  to  the  perfection  of 


CARBURETION,  CARBURETERS  AND  VAPORIZKRS  43 

satisfactory  apparatus  to  carburet  air.  Successful  working  of  such 
an  engine  is  dependent  upon  the  reliability,  certainty,  and  satis- 
factory working  of  the  carbureting  device.  Carburetion  cannot 
be  carried  on  at  ordinary  temperatures  unless  the  fuel  is  very 
volatile.  For  the  less  volatile  fuels  heat  is  employed  as  an  aid,  and 
in  this  case  carburetion  consists  of  atomization  and  subsequent 
vaporization  by  heat. 

The  method  adopted  depends  upon  the  fuel  to  be  used,  therefore 
carburetion  will  be  treated  under  the  following  five  heads :  ( 1 )  gas ; 
(2)  gasoline;  (3)  kerosene;  (4)  alcohol;  and  (5)  oil. 

1.  Gas.     Gas  obtained  from  a  city  main  is  ready  for  use  as  de- 
livered, but  if  a  pure  gas  is  supplied,  it  must  be  prepared  for  com- 
bustion by  intimately  mixing  with  air.    This  may  be  accomplished 
by  puanping  the  gas  and  air  together  into  the  cylinder  or  into  the 
space  outside  the  admission  valve.     This  method  is  illustrated  by 
the  Koerting  engine  in  Chapter  X.     Another  method  is  to  intro- 
duce the  gas  and  air  into  the  cylinders 'through  separate  valves. 

2.  Gasoline.     This  being  one  of  the  most  frequently  used  fuels, 
its  carburetion  will  be  treated  at  length.     It  may  be  carried  on  by 
three  distinct  methods,  the  first  two  of  which  have  practically  fallen 
into  disuse. 

a.  Surface  Carburetion.  This,  the  earliest  method  used,  con- 
sists of  evaporating  the  liquid  hydrocarbon  by  passing  a  current  of 
air  over  the  surface  of  the  liquid.  The  air  thus  becomes  saturated 
by  evaporation  of  the  liquid  from  its  free  surface.  This  method  is 
practically  obselete  for  the  following  reasons :  Evaporation  from 
the  free  surface  of  gasoline  will  tend  to  volatilize  the  lighter  hydro- 
carbons, leaving  a  liquid  of  rapidly  increasing  density,  which  finally 
loses  its  volatility  at  ordinary  temperatures.  The  continued  evap- 
oration reduces  the  temperature  of  the  liquid,  due  to  its  latent  heat, 
and  this  also  reduces  its  volatility.  Even  if  fuel  be  constantly 
added  to  the  carbureter  to  replace  that  evaporated,  a  uniform  mix- 
ture is  impossible. 

6.  Mechanical  Ebullition.  By  introducing  a  current  of  air  below 
the  surface  of  gasoline  and  allowing  it  to  bubble  to  the  surface  a 
certain  amount  of  the  liquid  is  entrained  as  mist  in  the  air.  This 


44  INTERNAL  COMBUSTION  ENGINE  MAMAL 

method  was  abandoned  also  for  practically  the  same  reasons  as  the 
former. 

c.  Spray  Carburetion.  This  is  the  only  practical  method  now  em- 
ployed to  convert  gasoline  into  a  combustible  vapor.  Each  suction 
stroke  of  the  piston  creates  a  vacuum  in  the  cylinder,  which  vacuum 
sucks  the  air  into  the  cylinder  through  the  mixing  chamber  of  the 
carbureter.  This  air  is  at  a  pressure  below  the  atmosphere.  The 
mixing  chamber  communicates  with  the  gasoline  chamber  of  the 
carbureter  by  a  fine  nozzle  or  needle  valve.  As  the  air  passes  over 
this  nozzle  a  spray  of  gasoline  is  sucked  through  it  into  the  pass- 
ing air  which  it  saturates.  This  is  made  more  clear  by  a  study  of 
the  carbureter  itself. 

A  good  carbureter  or  mixing  valve  must  fulfill  the  following  re- 
quirements: It  must  be  adjustable  so  that  the  correct  proportion 
of  fuel  and  air  is  obtained;  this  proportion  must  be  maintained  at 
varying  speeds;  if  possible,  the  location  of  the  spraying  nozzle 
should  be  near  the  middle  'of  the  air  passage;  and  the  apparatus 
must  be  simple  and  compact. 

The  distinction  between  a  mixing  valve  and  a  carbureter  will  be 
seen  from  a  description  of  each.  In  both  cases  fuel  is  drawn 
through  a  nozzle  into  the  air  which  is  being  sucked  into  the  cylin- 
der. A  mixing  valve  has  its  nozzle  below  the  source  of  fuel  supply 
and  this  nozzle  is  opened  and  closed  by  a  valve  which  is  lifted  at 
each  aspiration  stroke  of  the  cylinder.  A  carbureter  has  its  nozzle 
just  above  the  gasoline  level  in  the  gasoline  chamber  of  the  car- 
bureter and  the  fuel  is  sucked  through  the  nozzle  by  the  air  on  each 
aspiration  stroke.  In  either  case  the  flow  of  gasoline  vapor  stops 
when  the  engine  is  stopped. 

The  Schebler  Carbureter,  Figs.  27  and  2?a.  This  is  one  of  the  most 
popular  and  efficient  of  the  high-speed  carbureters.  The  opening 
marked  "gasoline  supply"  is  connected  to  the  gasoline  tank  by  pip- 
ing. Gasoline  enters  here  and  goes  to  the  annular  gasoline  chamber. 
It  is  maintained  at  a  constant  level  in  this  chamber  by  means  of  a 
cork  float  and  a  float  valve  connected  to  this  float.  The  connection 
is  pivoted  so  that  the  valve  will  rise  as  the  float  falls.  As  the  gaso- 
line level  drops  the  cork  float  on  its  surface  drop:*  and  this  opens 


4:6  INTERNAL  COMBUSTION  ENGINE  MANUAL 

the  float  valve,  allowing  gasoline  to  enter.  When  the  gasoline  rises 
to  the  proper  level  the  float  closes  the  valve.  The  upper  end  of  the 
carbureter,  which  contains  the  throttle  discx  is  connected  to  the 
admission  pipe  of  the  engine.  On  each  suction  stroke  air  is  sucked 
through  the  air  passage  into  the  mixing  chamber.  In  its  course  it 
passes  around  the  spray  nozzle.  This  nozzle  passes  through  the 
air  passage  wall  and  communicates  with  the  gasoline  chamber. 
Each  suction  stroke,  gasoline  is  sucked  through  the  spray  nozzle  and 
mixes  with  the  air  in  the  mixing  chamber.  The  opening  of  this 
spray  nozzle  can  be  regulated  by  a  needle  valve,  Fig.  27 a,  The 
carbureter  is  designed  so  that  the  air  passage  will  supply  enough  air 
at  the  low  speeds.  As  the  speed  is  increased  above  this,  it  is  evident 
that  more  fuel  is  sucked  through  the  needle  valve  and  hence  more 
air  must  be  supplied  per  stroke  for  combustion.  The  leather  air 
valve  shown  on  the  right,  Fig.  27,  compensates  for  this  as  follows: 
At  low  speeds  the  valve  is  kept  on  its  seat  by  the  spring.  As  the 
suction  increases  it  overcomes  the  tension  of  this  spring  and  the 
valve  will  lift  each  aspiration  stroke  an  amount  dependent  upon  the 
speed.  The  throttle  disc  acts  as  an  ordinary  throttle,  but  attach- 
ments on  the  throttle  shaft  further  regulate  the  fuel  supply  for  the 
speed.  As  the  disc  is  opened  and  more  air  is  drawn  through  the 
air  passage,  it  becomes  necessary  to  provide  a  larger  fuel  valve 
opening  to  supply  the  increased  demand  for  fuel.  This  is  ac- 
complished as  follows:  As  the  throttle  disc  is  opened  the  cam  on 
the  adjusting  cam  casting  is  rotated  and  bearing  on  the  needle  valve 
roller  opens  or  shuts  the  needle  valve  simultaneous  with  the  throttle. 
The  needle  valve  roller  moves  the  needle  valve  lever  and  the  needle 
valve  about  the  needle  valve  lever  pin,  thus  opening  and  closing 
the  needle  valve,  Fig.  27 a.  The  cam  spring  adjusters  are  used  to 
adjust  the  cam  on  the  adjusting  cam  casting  so  that  the  needle 
valve  roller  pin,  and  consequently  the  needle  valve,  will  be  opened 
the  proper  amount  at  all  speeds.  The  adjustments  are  too  compli- 
cated for  a  novice  to  handle.  A  drain  cock,  not  shown,  is  generally 
placed  on  the  bottom  of  the  bowl  to  drain  the  gasoline  chamber. 
This  prevents  the  accumulation  of  water  and  dirt  in  the  carbureter. 
All  metal  parts  are  of  brass.  The  end  of  the  spray  nozzle  is  in  the 


CABBURETION,  CARBURETERS  AND  VAPORIZERS  47 

center  of  the  column  of  entering  air.  This  is  a  point  that  is  over- 
looked in  many  otherwise  good  designs,  and  tends  to  maintain  a 
uniform  quality  mixture  for  all  positions  of  the  carbureter  and  is 
of  importance  in  marine  practice  as  well  as  in  motor  vehicles. 


FIG.  28. — Limkenheimer  Mixing  Valve. 


The  Lunkenheimer  Mixing  Valve,  Fig.  28.  Air  entrance  is 
effected  at  1.  Gasoline  enters  at  3  through  the  needle  valve  passage 
4.  The  amount  of  entering  fuel  is  regulated  by  the  needle  valve 
which  is  operated  by  the  graduated  wheel  5.  The  mixture  leaves  for 
the  engine  at  2,  after  passing  over  the  baffle  6  which  aids  the  mixing. 
On  each  aspiration  stroke  valve  7  lifts,  uncovering  the  needle  valve 


48  INTERNAL  COMBUSTION  ENGINE  MANUAL 

passage.  Air  is  sucked  to  the  upper  chamber,  drawing  gasoline 
from  the  needle  valve.  The  valve  is  seated  by  its  spring  at  the  end 
of  the  aspiration  stroke,  and  its  lift  is  regulated  by  the  stop  8. 
Passage  2  contains  a  throttle. 

There  are  innumerable  carbureters  and  mixing  valves  on  the 
market  and  the  above  are  chosen  as  typical  designs. 

General.  It  is  advantageous,  especially  in  cold  weather,  to  have 
the  source  of  air  supply  warmer  than  the  atmosphere.  Many  methods 
are  employed,  such  as  having  the  air  suction  drawn  from  the 
proximity  of  the  hot  exhaust  pipe,  leading  the  hot  exhaust  gases 
around  the  admission  pipe,  or  jacketing  the  carbureter  with  the 
exhaust  gases  or  heated  exhaust  circulating  water.  80°  F.  to  85°  F. 
is  the  best  temperature  for  admission.  The  temperature  and  hygro- 
metric  condition  of  the  air  supply  regulate  the  relative  quantities 
of  air  and  fuel  required  in  the  mixture.  It  will  be  necessary  to 
regulate  the  mixture  to  meet  the  varying  atmospheric  conditions. 

3.  Kerosene.  There  are  two  methods  of  treating  this  fuel:  (a) 
carburetion,  similar  to  gasoline;  and  (b)  injecting  into  the  cylinder 
or  vaporizer  near  the  air  valve,  as  in  the  case  of  the  heavier  oils. 

a.  Carburetion  of  kerosene,  as  stated  before,  requires  the  appli- 
cation of  heat  to  aid  vaporization  at  ordinary  temperatures.    There- 
fore, the  process  consists  of  two  parts,  first  atomizing  the  fuel  in  a 
similar  manner  to  gasoline  carburetion  and  then  vaporizing  this 
spray  by  heating.    This  heat  is  applied  either  by  jacketing  the  car- 
bureter or  admission  pipe,  or  by  heating  the  air  before  passing  the 
same  through  the  carbureter.     Any  well   designed   gasoline  car- 
bureter will  carburet  kerosene  if  jacketed.     Many  kerosene  car- 
bureters start  on  gasoline  and  shift  to  kerosene  after  the  engine  is 
started  and  well  warmed  up.     Such  a  carbureter  is  similar  to  the 
alcohol  carbureter  shown  in  Fig.  30. 

b.  Kerosene  may  be  injected  into  the  cylinder  direct   and  the 
necessary  air  supplied  by  a  separate  valve.     'Means  are  employed 
to  regulate  the  amount  of  fuel  that  is  drawn  into  the  cylinder  each 
suction  stroke.    The  passage  of  fuel  through  its  valve  atomizes  it, 
and  upon  contact  with  the  hot  cylinder  or  vaporizer  walls  it  is 
vaporized. 


CABBURETION,  CARBURETERS  AND  VAPORIZERS 


49 


The  Crossley  vaporizer  (see  Fig.  29).  Air  is  drawn  into  the 
cylinder  by  the  suction  stroke  of  the  engine,  through  the  spring 
loaded  air  valve.  As  this  valve  lifts,  the  in-rush  of  air  sucks  a  kero- 
sene spray  through  the  duct  labeled  oil  measurer.  The  lamp  flame 
serves  to  vaporize  the  atomized  kerosene,  in  addition  to  heating 
the  hot  tube  igniter,  c  is  the  cylinder,  and  w  is  the  water  jacket. 
When  running  the  vaporizer  temperature  is  maintained  by  the  heat 
of  compression. 


FIG.  29. — Crossley  Vaporizer. 

4.  Alcohol.  Correct  carburetion  of  alcohol  is  more  difficult  than 
would  be  suspected  by  an  inexperienced  operator.  Excess  of  air 
creates  increased  loss  of  heat  through  the  exhaust  gases  and  retards 
ignition,  but  a  deficiency  of  air  causes  much  more  serious  trouble. 
The  resulting  incomplete  combustion  causes  the  formation  of  cor- 
rosive and  fouling  products  which  corrode  and  clog  the  cylinders, 
valves,  etc.  Like  kerosene,  alcohol  requires  auxiliary  heat  for  vapor- 
ization, although  some  few  carbureters  have  been  built  without  pro- 
vision for  heating  the  atomized  product.  The  heat  may  be  applied 
by  any  of  the  ways  enumerated  under  kerosene.  'The  future  form 
of  carbureter  for  alcohol  seems  problematical,  but  a  likely  type  is 
shown  in  Fig.  30.  This  carbureter,  known  as  the  double  float  type, 
is  constructed  to  use  either  gasoline  or  alcohol,  thus  permitting  the 


50 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


start  to  be  made  on  gasoline  (which  will  volatilize  cold)  and  sub- 
sequent running  to  be  done  on  alcohol.  Suppose  that  compartment 
&  is  used  for  gasoline,  and  a  for  alcohol,  c  and  d  are  floats  in  these 
chambers  that  regulate  the  level  of  liquid  in  the  chambers  by  open- 
ing and  closing  the  needle  valves  g  and  In.  e  and  /  are  springs  that 
can  be  used  to  keep  either  needle  valve  (g  or  h)  closed  when  the 


Gasoline. 


Alcohol. 


FIG.  30. — Alcohol  Carbureter. 


other  is  in  use.  j  and  Ic  are  nozzles  communicating  with  the  fuel 
chambers  b  and  a.  m  is  the  air  inlet  and  n  is  a  valve  which  can  be 
rotated  so  as  to  connect  the  air  inlet  m  with  the  admission  pipe  a 
by  way  of  either  j  or  k.  o  is  the  admission  pipe  to  the  engine1  and  p 
is  a  throttle.  The  carbureter  is  shown  with  both  needle  valves 
closed. 

The  operation  is  as  follows:    Using  gasoline  to  start,  push  aside 
the  spring  e  allowing  the  float  c  to  operate  and  admit  gasoline  to  6. 


GiBBUBBTION,    CARBURETERS    AXD    VAPORIZERS  51 

With  the  valve  n  in  the  position  shown,  the  apparatus  becomes  a 
simple  float  valve  gasoline  carbureter.  The  air  is  drawn  in  through 
m  over  j,  sucking  up  gasoline  vapor,  through  n  and  out  at  o.  When 
the  engine  is  warm  and  it  is  desired  to  shift  to  alcohol,  the  spring 
e  is  pushed  to  the  closed  position  and  f  is  pushed  aside,  allowing 
the  float  d  to  operate.  The  valve  n  is  turned  so  as  to  connect  m  and 
o  by  way  of  k.  We  now  have  a  simple  float  valve  alcohol  car- 
bureter, the  air  being  drawn  into  m  over  fc,  sucking  up  alcohol 
vapor,  and  going  out  by  way  of  n  and  o.  This  type  of  vaporizer  is 
supplied  with  preheated  air. 

5.  Oil.  Heavy  oils,  those  heavier  than  kerosene,  are  generally 
sprayed  directly  into  the  cylinder.  Air  is  forced  through  a  separate 
valve  into  the  cylinder  either  with  or  ahead  of  the  fuel.  Upon 
coming  into  contact  with  the  hot  cylinder  or  its  contained  hot  air 
the  atomized  oil  is  vaporized.  One  of  the  most  difficult  features  of 
design  connected  with  the  "  heavy  oil "  engines  is  to  reduce  the 
deposits  of  carbon  that  tend  to  form.  When  a  heavy  oil  is  volatilized 
there  is  a  strong  tendency  toward  chemical  change.  Its  heavy 
hydrocarbon  constituents  tend  to  decompose  into  lighter  ones.  This 
reaction,  called  "  cracking/'  which  is  absent  when  the  lighter  fuels 
are  carbureted  leaves  a  carbon  residue.  The  Diesel  engine,  which 
is  described  in  Chapter  X,  is  probably  the  most  interesting  type  of 
oil  engine.  As  its  operation  is  described  later  it  is  omitted  here. 


CHAPTER  VI 
IGNITION 

Next  to  carburetion,  the  most  important  feature  in  internal  com- 
bustion engine  operation  is  proper  ignition.  The  abandonment  of 
naked  flame  ignition  because  of  its  uncertainty  leaves  three  general 
methods  of  igniting  the  compressed  mixture:  (1)  the  electric  spark; 
(2)  by  contact  of  the  mixture  with  a  heated  tube;  (3)  by  com- 
pressing the  charge  until  its  temperature  reaches  the  point  of 
ignition. 

The  first  method,  that  of  the  electric  spark,  is  the  one  in  most 
common  use,  the  reason  being  that  it  has  reached  a  nearly  perfect 
state  of  development  and  it  can  be  more  easily  "  timed."  By  timing 
the  spark  is  meant  regulating  the  point  in  the  stroke  at  which  igni- 
tion takes  place.  For  high-speed  engines  electrical  ignition  is  the 
only  one  flexible  enough  for  accurate  regulation.  It  is  obvious  that 
with  an  engine  running  at  600  revolutions  per  minute,  the  stroke 
being  but  1/20  second,  it  would  be  extremely  difficult  mechanically 
to  vary  to  a  nicety  the  point  in  the  stroke  at  which  ignition  will 
take  place. 

Electric  Spark.  By  shooting  a  hot  electric  spark  through  a  com- 
pressed charge  ignition  will  take  place.  Electrical  ignition  may  be 
subdivided  into  two  classes:  (1)  jump  spark  system;  (2)  make  and 
break  system. 

1.  Jump  Spark.  This  system  requires  among  other  things  a 
spark  plug,  which  is  shown  in  the  circuit  in  Fig.  31.  A  current  of 
high  potential  is  made  to  jump  across  a  gap  between  two  terminals 
of  the  spark  plug.  This  plug,  which  is  screwed  into  the  cylinder 
head,  has  its  gap  surrounded  by  the  compressed  mixture  at  the 
moment  of  ignition.  Closing  the  circuit  causes  the  spark  to  leap 
and  this  ignites  the  charge. 

A  Single  Cylinder  Ignition  Circuit  is  shown  in  Fig.  31.  The 
spark  plug  is  screwed  into  the  cylinder  head  b.  The  plug  consists 
of  the  steel  casing  a  which  screws  into  the  cylinder  head  &  and  thus 
the  terminal  g  is  grounded  at  the  engine.  The  other  terminal  h 


IGNITION  53 

is  insulated  from  the  rest  of  the  plug  by  the  porcelain  collars  c  and 
d.  f  is  a  gas  tight  washer  of  asbestos.  These  collars  and  washers 
are  made  in  a  variety  of  shapes  and  of  different  materials,  but  the 
principle  is  the  same  in  all  cases. 

The  system  consists  of  two  circuits,  a  primary  and  a  secondary. 
Following  the  primary  circuit,  shown  by  the  heavy  line,  it  goes  from 
the  ground  J  through  the  battery  K  to  the  buzzer  L,  through  the 


FIG.  31. — Single  Cylinder  Jump  Spark  Ignition  Showing  Details  of 

Spark  Plug. 

primary  windings  of  the  coil  M  to  the  terminal  N  of  the  timer. 
The  timer  shaft  0  revolves,  and  this  shaft  being  grounded,  the 
circuit  is  completed  by  the  cam  on  the  shaft.  The  secondary  circuit 
leads  from  the  ground  P  through  the  secondary  winding  of  the  coil 
M  to  the  terminal  r  of  the  spark  plug  then  down  the  spindle  s  to 
the  point  h.  The  point  g  being  grounded,  the  circuit  is  completed 
by  the  gap  between  the  two  points  of  the  plug.  When  the  primary 
circuit  is  completed  by  the  timer,  sending  current  through  the 
primary  windings  of  the  coil,  a  high  tension  current  is  induced  in 
the  secondary  windings  and  this  current  is  strong  enough  to  over- 
come the  resistance  of  the  gap,  which  it  leaps,  t  is  a  condenser 
connected  across  the  terminals  of  the  buzzer.  Its  function  is  to 
damp  the  break  spark  at  L. 
5 


54  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Magnetos.  The  foregoing  system  uses  battery  current.  A  "  high 
tension  "  magneto,  which  is  an  apparatus  similar  to  a  dynamo,  may 
furnish  the  current.  In  this  case  the  magneto  furnishes  the  current 
direct  to  the  plug,  the  battery  and  coil  being  eliminated.  If  a  "  low 
tension  magneto  "  is  used,  the  current  must  be  stepped  up  by  the 
use  of  a  small  coil  or  "  booster."  In  this  case  the  buzzer  is  elimi- 


FIG.  32a .— Wiring  of  Coils.    FIG.  32.— Wiring  for  Four  Cylinder, 

Jump  Spark  Ignition. 


nated.  The  function  of  the  buzzer  is  to  break  up  the  spark  at  the 
gap  into  a  vibrating  series,  thus  increasing  the  certainty  of  ignition. 

Multicylinder  •< ignition,  Fig.  32,  illustrates  four-cylinder  engine 
wiring. 

Fig.  32a  shows  the  wiring  of  the  coil.  The  timer  shaft  h  re- 
volves, making  contact  with  the  terminals  g19  g2,  g3,  g±  in  succession. 


h  is  grounded  to  the  engine,    a,  6t,  b2,  & 


are  plugs 


on  the  outside  of  the  coil  box  and  are  connected  as  shown  in  Fig. 
32a.    The  plug  a  connects  to  the  battery,  d  to  the  ground,  e±,  e2, 


IGNITION 


55 


'  etc.,  to  the  spark  plugs,  and  frj,  &2,  etc.,  to  the  terminals  g19  g2)  etc., 
of  the  timer.  &1?  Ic2,  etc.,  are  the  spark  plugs.  cly  c2,  etc.,  are  the 
buzzers.  The  shaft  li  being  in  the  position  shown,  the  primary 
circuit  goes  from  ground  ~k,  through  g±  to  &1?  through  vibrator  ct 
and  primary  windings  of  coil  1  to  plug  a,  thence  to  battery  and 
ground.  The  secondary  circuit  1  leads  from  ground  L  to  plug  d, 
through  secondary  windings  of  coil  1,  where  a  high  tension  current 
is  induced,  to  plug  elf  thence  to  spark  plug  Te^.  This  circuit  is  simi- 
lar to  the  one  cylinder  circuit  described  above.  When  shaft  h  is 


FIG.  33. — Splitdorf  Timer,  Wipe  Contact  Type. 

revolved  to  make  contact  with  g2,  the  current  flows  through  coil  2 
to  spark  plug  &2,  etc.,  and  in  this  manner  the  cylinders  are  ignited 
in  rotation. 

The  Timer.  Means  must  be  employed  with  a  multicylinder 
engine  to  ignite  each  cylinder  in  turn  at  precisely  the  proper  in- 
stant. This  is  accomplished  by  the  timer.  It  is  interposed  in  the 
primary  circuit  with  a  terminal  for  each  primary  wire  from  the  coil, 
Fig.  32.  There  are  two  general  types  of  timers,  the  wipe  contact  and 
the  La  Costa  or  roller  contact  type.  Fig.  33  shows  the  construc- 
tion of  the  Splitdorf  wipe  contact  type.  The  shaft  A,  which  is 
grounded,  has  secured  to  it  a  head  which  carries  the  spring  point  B. 


56  INTERNAL  COMBUSTION  ENGINE  MANUAL 

As  the  shaft  A,  which  is  driven  by  gearing  generally  from  the  cam 
shaft,  revolves,  the  point  B  makes  contact  with  the  terminals  C,  D, 
etc.,  in  turn.  These  terminals  are  insulated  from  the  collar  of  the 
timer  E.  When  contact  is  made  with  any  terminal,  the  primary 
circuit  corresponding  to  that  terminal  is  completed  and  the  corre- 
sponding cylinder  is  fired.  The  shaft  A  runs  on  ball  bearings  F. 
The  collar  E,  which  carries  the  several  terminals,  can  be  shifted  by 
the  lever  G  to  advance  or  retard  the  spark.  The  spindle  H  holds 


PIG.  34. — Splitdorf  Timer,  La  Costa  Type. 

the  cover  on  the  timer.    This  is  a  similar  type  to  the  timer  on  the 
two  cylinder  engine  in  the  laboratory. 

Fig.  34  illustrates  the  La  Costa  type  of  timer.  The  shaft  A, 
which  is  revolved  by  gearing  from  the  cam  shaft,  is  grounded,  and 
carries  the  roller  contact  F.  The  terminals  Bf  C,  D  and  Ef  are  in- 
sulated from  the  rest  of  the  timer.  The  primaries  for  each  cylinder 
lead  from  the  coil  to  these  terminals.  As  the  roller  F  makes  con- 
tact with  the  plates  G  of  each  terminal  it  completes  the  primary 
circuit  of  the  cylinder  corresponding,  firing  each  cylinder  in  turn. 
The  spark  can  be  advanced  or  retarded  by  rotating  the  collar  carry- 
ing the  terminals  by  means  of  a  lever  attached  to  H. 


IGNITION 


57 


2.  Make-and-Break  System.  This  system,  which  is  a  mechanico- 
electrical  one  requiring  cam  or  other  gearing  to  make  and  break  a 
contact  inside  the  cylinder,  is  applicable  to  slow  speed  engines,  and 
for  this  special  duty  has  some  advantages  over  the  jump  spark.  A 
moving  contact  in  the  electrical  circuit  is  mechanically  made  and 
broken  inside  the  cylinder.  At  the  break  a  spark  will  leap  between 


FIG.  35. — Circuit  for  Make  and  Break  Ignition. 

the  contacts  igniting  the  mixture.  This  system  admits  of  two 
methods:  (1)  the  wipe  spark;  (2)  the  hammer  break.  By  the  first 
method  the  contacts  are  made  to  brush  together  and  by  the  second 
the  contacts  are  brought  together  sharply  and  separated.  The  wir- 
ing for  both  methods,  shown  in  Fig.  35,  is  similar.  A  small  coil  is 
employed  to  step  up  the  current,  but  no  vibrator  is  used  as  this 
would  cause  a  spark  to  occur  at  make  as  well  as  break,  thus  probably 
igniting  the  charge  prematurely.  The  circuit  shown  admits  of 
battery  or  magneto  current. 


58 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


The  wipe  spark  mechanism  is  shown  in  Fig.  36.  The  rod 
&  oscillates  the  collar  a  hy  means  of  the  cam  c  on  the  countershaft. 
The  collar  a  carries  the  contact  point  d,  grounded  to  the  engine. 
As  the  collar  a  oscillates  the  point  d  wipes  past  the  spring  point  e 


FIG.  36. — Wipe  Spark  Igniter. 

completing  the  circuit.  The  spring  g  quickly  returns  the  collar  to 
its  original  position  when  the  cam  releases  the  rod,  and  the  circuit 
thus  being  broken  a  spark  will  occur  between  the  points  d  and  e. 
The  source  of  current  is  connected  to  e  by  the  terminal  /.  Terminal 
f  and  point  e  are  insulated  from  the  rest  of  the  mechanism.  The 
advantage  of  the  wipe  spark  over  the  hammer  break  lies  in  the  fact 
that  the  sliding  contact  prevents  carbon  deposits  on  the  points. 


IGNITION 


59 


Hammer  Break.  The  principle  of  the  hammer  break  is  shown 
in  Fig.  37.  The  spindle  a,  carrying  the  contact  b,  is  actuated  by 
cam  and  rod  through  the  lever  c.  d  is  a  spring  to  keep  b  against  the 
collar.  /  is  the  cylinder  head.  Contact  b  is  grounded  to  the  cylin- 
der. Contact  e  is  insulated  from  the  cylinder  and  its  terminal  g  is 
connected  to  the  source  of  current.  When  the  contacts  e  and  & 
are  separated  mechanically,  a  spark  occurs.  The  cam  actuating  this 
gear  is  generally  situated  on  the  countershaft  of  the  engine. 


FIG.  37. — Hammer  Break. 


60  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Advantages  and  Disadvantages  of  the  Different  Electrical  Systems 

The  make-and-break  system  is  the  simpler  electrically  and  less 
trouble  occurs  from  insulation  and  short  circuits  because  a  low 
tension  current  is  used  throughout.  It  is  mechanically  more  com- 
plex, hence  is  more  suitable  for  low-speed  engines,  and  hard  to 
adapt  to  high-speed  engines. 

Although  electrically  more  complex  than  the  make-and-break 
system,  the  jump  spark  system  has  no  moving  parts  inside  the 
cylinder,  and  its  flexibility  as  regards  spark  adjustment  makes  it 
the  universal  system  for  high-speed  engines. 

General.  All  contact  points  and  the  points  of  a  spark  plug  are 
made  of  a  platinum  alloy  or  other  heat  resisting  conductor.  The 
points  must  be  kept  clean  and  free  from  carbon,  as  this  formation 
tends  to  form  short  circuits  across  the  gap,  thus  damping  the  spark. 
All  connections  should  be  so  arranged  that  they  cannot  jar  loose  and 
the  insulation  must  be  protected  from  heat,  oil,  and  especially  water. 

Dual  Ignition.  By  a  "  dual  ignition  "  system  is  meant  one  in 
which  the  current  is  supplied  from  either  a  battery  or  magneto,  or 
from  both,  at  will.  Some  systems  have  a  separate  set  of  spark  plugs 
for  each  source  of  current  supply  and  in  this  case  the  system  is  in 
effect  two  separate  systems.  The  dual  ignition  system  proper,  in 
which  current  may  be  obtained  through  one  set  of  plugs  from  either 
battery  or  magneto,  is  shown  in  Fig.  38. 

F  is  a  four  way  switch  which  operates  as  follows :  Connecting 
a  and  b,  the  current  goes  from  the  dynamo  to  the  primary  of  the 
coil  direct  where  it  is  converted  to  a  high  tension  current.  Connect- 
ing a  and  d  the  current  goes  from  the  battery  direct  to  the  primary 
of  the  coil.  Connecting  c  and  d  the  voltage  of  the  battery  can  be 
read  by  a  volt-ammeter  in  the  circuit.  The  secondary  circuit  s  is 
similar  to  that  shown  in  Figs.  32  and  32a, 

This  should  not  be  confused  with  double  ignition,  in  which  there 
are  two  separate  circuits  and  sets  of  spark  plugs,  one  for  the  battery 
and  one  for  the  magneto. 

There  is  a  tendency  in  modern  practice  to  have  two  spark  plugs 
for  each  cylinder,  so  as  to  ignite  the  charge  at  two  points  simul- 
taneously. This  is  theoretically  excellent  as  it  will  accelerate  flame 


IGNITION 


61 


propagation,  but  there  are  several  difficulties  that  are  hard  to  over- 
come. First,  the  two  sparks  must  occur  at  correctly  timed  in- 
stants, otherwise  the  object  of  the  system  would  be  defeated. 
Second,  if  the  two  spark  plugs  are  situated  close  together  little 
benefit  is  derived.  The  first  difficulty  has  been  overcome  by  several 
manufacturers  of  ignition  specialties,  and  where  design  permitted 
the  installation  of  two  spark  plugs  widely  separated,  the  author  has 
heard  of  some  remarkable  results. 


"K 

^  — 
Dy/t 

p 
a/no 

FIG.  38. — Dual  Ignition  Circuit. 

Master  Vibrator.  A  variety  of  spark  coil  recently  placed  on  the 
market  is  fitted  with  what  is  called  a  master  vibrator.  In  this  coil 
there  is  one  common  buzzer  for  the  coils  of  all  cylinders.  The  sys- 
tem shown  in  Fig.  32a  could  be  modified  as  follows:  cut  out  all 
the  buzzers  shown  and  lead  the  primary  directly  from  the  timer  to 
the  coil.  Insert  a  buzzer  (master  vibrator)  in  the  common  primary 
line  from  the  plug  a.  The  advantage  of  this  system  lies  in  the  fact 
that  the  vibrators  give  more  trouble  than  any  other  part  of  the 
ignition  system,  for  an  arc  is  constantly  present  that  burns  and 
fouls  the  vibrator  contacts,  and  obviously  one  vibrator  is  easier  to 
keep  clean  and  adjusted  than  are  four. 


62 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


Hot  Tube  Ignition.  Although  rapidly  being  superseded  by  the 
electrical  systems,  the  hot  tube  is  still  being  furnished  by  some 
manufacturers.  A  typical  hot  tube  igniter  is  shown  in  Fig.  39. 
One  end  of  a  small  tube  communicates  with  the  cylinder,  the  other 
end  is  closed.  A  Bunsen  burner,  located  in  a  surrounding  chimney, 
keeps  part  of  the  tube  at  a  red  heat.  The  chimney  is  partially  lined 
with  asbestos  or  other  non-conductor,  which  reduces  loss  of  heat  by 
radiation. 


FIG.  39.— Hot  Tube  Igniter 

On  the  exhaust  stroke  the  tube  is  filled  with  exhaust  gases.  On 
the  suction  stroke  part  of  these  gases  remain  in  the  tube.  On  the 
compression  stroke  the  exhaust  gases  are  compressed  into  the  closed 
end  of  the  tube  and  some  fresh  mixture  is  compressed  into  the 
cylinder  end  of  the  tube.  When  the  fresh  charge  reaches  the  hot 
part  of  the  tube  it  ignites,  and  near  the  dead  center,  when  the 
velocity  of  flame  propagation  exceeds  the  velocity  of  the  entering 
mixture,  explosion  takes  place.  The  point  of  ignition  may  be  varied 
by  shifting  the  chimney  carrying  the  Bunsen  burner  along  the  tube 
by  use  of  the  set  screw  shown.  Accurate  timing  for  slow-speed 


IGNITIOX 


63 


engines  is  obtained  by  inserting  a  valve  at  the  cylinder  end  of  the 
tube.  By  opening  this  valve  at  the  correct  point  in  the  stroke  the 
fresh  mixture  comes  in  contact  with  the  hot  tube.  The  valve  is 
actuated  by  cam  gear  from  the  countershaft. 

Ignition  by  Compression.  When  a  gas  is  compressed  its  tem- 
perature rises  and  it  is  possible  to  compress  the  mixture  to  the  point 
of  ignition.  There  are  two  distinct  methods  of  applying  this 
principle. 

a.  By  the  Diesel  method  air  is  compressed  in  the  cylinder  until 
its  temperature  is  far  above  the  ignition  point  of  the  fuel  and  the 
fuel  is  injected  into  this  heated  air  during  the  working  stroke. 


"  ' 


FIG.  40. — Ignition  by  Compression. 

6.  The  second  method,  sometimes  known  as  the  hot  bulb  method, 
is  shown  in  Fig.  40.  A  bulb  a  on  the  cylinder  head  is  maintained 
at  ignition  temperature  by  the  heat  of  compression.  This  bulb  is 
generally  encased  (not  shown  in  figure)  to  reduce  loss  of  heat  by 
radiation.  To  start  the  engine  the  bulb  must  be  heated  by  an  out- 
side flame.  When  gas  is  the  fuel,  the  iube  b  is  omitted  and  the 
action  is  similar  to  the  hot  tube.  The  compression  is  so  regulated 
that  on  the  compression  stroke  the  velocity  of  flame  propagation 
will  exceed  the  velocity  of  gases  entering  the  neck  of  the  bulb  at 
the  proper  point  in  the  stroke  for  ignition.  For  oil  fuel  the  tube  b 
is  used,  air  entering  the  admission  valve  and  oil  fuel  at  6.  The  hot 
tube  acts  as  a  vaporizer.  Timing  the  point  of  ignition  is  accom- 
plished by  regulating  the  compression  pressure. 


CHAPTER  VII 
COOLING  AND  LUBRICATION 

Cooling  the  Gases,  One  of  the  measures  of  efficiency  for  an 
internal  combustion  engine  is  the  effective  -utilization  of  the  avail- 
able heat  energy.  This  in  turn  depends  upon  the  initial  and  final 
temperatures  of  the  gases  that  develop  the  pressure,  if  these  gases 
be  cooled  as  far  as  possible  by  transforming  their  heat  into  work. 
Experiments  have  been  made  along  the  line  of  injecting  water  into 
the  cylinder  both  before  and  after  ignition  of  the  charge,  on  the 
theory  that  the  heat  absorbed  from  the  ignited  mixture  would 
vaporize  the  water  and  reappear  as  work  on  the  piston  in  the  form 
of  pressure  due  to  adiabatic  expansion  of  the  water  vapor.  Although 
this  reduces  the  loss  of  heat  in  the  exhaust,  it  is  open  to  the  objec- 
tion that  it  reduces  the  net  effective  pressure.  It  is  not  in  common 
use. 

Cooling  the  Cylinder.  Due  to  the  high  heat  developed  by  the 
combustion  of  the  mixture  it  becomes  necessary  to  cool  the  metal 
of  the  cylinder  walls,  pistons,  valves,  etc.  Were  this  temperature 
not  reduced  the  result  would  be  leaky  valves,  deformations,  defective 
alignment,  seizing  of  piston,  and  oxidation  of  metal.  There  are 
two  methods  of  cooling  the  cylinder:  (1)  water  cooling;  (2)  air 
cooling. 

Water  Cooling.  The  cylinder  is  jacketed  and  water  is  circulated 
through  the  jacket.  Where  unlimited  water  is  available  the  exhaust 
is  lead  to  a  drain.  If  the  water  supply  is  limited  a  tank  is  em- 
ployed. Fig.  41  illustrates  the  use  of  a  tank  and  the  thermo-syphon 
system.  The  circulating  water  enters  at  the  bottom  of  the  jacket 
and,  as  it  becomes  heated, 'rises,  flowing  out  at  the  top  to  the  tank. 
A  continuous  circulation  is  thus  established.  When  this  system 
does  not  furnish  a  circulation  that  is  rapid  enough,  a  pump  is 
placed  in  the  supply  pipe  a.  For  slow  speed  engines  this  pump 
may  be  of  the  plunger  type,  if  the  water  is  free  from  foreign  par- 
ticles such  as  dirt  and  marine  growth,  or  of  the  centrifugal  type  if 
the  water  is  not  clear  as  in  marine  practice.  The  pump  is  designed 


COOLING  AND  LUBRICATION 


65 


for  the  probable  working  speed  because  one  that  would  supply 
sufficient  water  at  a  designed  high  working  speed  would  be  deficient 
at  low  speed,  and  one  that  was  designed  for  a  low  speed  might  cool 
the  cylinder  to  too  low  a  point  for  efficiency  at  high  speed. 


PIG.  41. — Thermo-Syphon  System. 


Fig.  42  shows  the  system  used  for  cooling  automobile  and  aero- 
plane engines,  where  only  a  small  amount  of  water  can  be  carried. 
The  radiator  shown  consists  of  a  top  and  bottom  header  connected 
by  vertical  tubes.  These  tubes  are  covered  with  thin  fins  to  increase 


PIG.  42. — Water  Cooling,  Radiator  and  Pump. 

their  radiating  surface.  The  water  enters  the  cylinder  jacket  at  the 
bottom,  flows  out  at  the  top,  heated,  and  returns  to  the  radiator 
where  it  is  cooled  by  passing  through  the  tubes.  The  circulation  is 
aided  by  a  pump,  and  a  fan  circulates  the  air  through  the  radiator 
between  the  tubes.  By  reusing  the  circulating  water  it  is  "  broken," 
that  is  the  salts  are  precipitated,  hence  there  will  result  less  sedi- 
ment in  the  jackets. 

Cooling  valves,  pistons,  etc.  In  all  large  size  engines  the  heat 
from  the  piston  will  not  radiate  to  the  cylinder  walls  rapidly  enough 
to  maintain  a  safe  piston  temperature.  This  necessitates  that  pro- 


66  INTERNAL  COMBUSTION  ENGINE  MANUAL 

vision  be  made  to  water  cool  the  piston.  Water  is  introduced  to 
hollows  cast  in  the  piston,  either  by  flexible  connections  or  by  two 
hollow  tubes  that  slide  through  a  stuffing  box  and  enter  chambers, 
one  of  which  contains  cool  water  under  pressure  and  the  other  of 
which  receives  the  heated  discharge  water. 

Admission  valves  are  kept  cool  by  the  cool  entering  mixture,  and 
where  practical  to  let  this  cool  mixture  impinge  on  the  exhaust  valve 
it  aids  in  maintaining  the  latter  at  a  safe  temperature.  The  cylin- 
der jackets  are  carried  as  near  as  possible  to  the  valve  seats.  Ex- 
haust valves  for  large  engines  are  generally  cast  hollow  and  are 
water  cooled,  the  circulating  water  entering  the  valve  through  a 
flexible  tube. 


FIG.  43. — Air  Cooled  Cylinder. 

Air  Cooling.  TChis  system  is  not  used  as  extensively  as  water  cool- 
ing. A  few  automobile  and  aeroplane  engines  and  all  motorcycle 
engines  are  air  cooled.  The  cylinder  is  cast  with  a  number  of  fins 
or  webs  on  its  outside  surface  to  increase  the  radiating  surface.  A 
fan  is  installed  to  increase  the  air  circulation  as  shown  in  Fig.  43. 
Fuel  economy  at  moderate  horse-power  and  speeds  is  higher  than 
in  the  water  cooled  system,  due  to  the  higher  cylinder  temperatures, 
but  as  the  engine  becomes  heated  the  horse-power  developed  falls 
below  that  which  should  be  developed  for  given  cylinder  dimensions. 
As  the  cylinder  dimensions  increase  it  becomes  more  difficult  to 
carry  off  the  heat  fast  enough  and  there  is  a  practical  limit  to  the 
size  engine  that  can  be  air  cooled. 

Lubrication 

The  external  lubrication  of  an  internal  combustion  engine  pre- 
sents no  novel  features  and  requires  no  comment,  but  the  internal 
lubrication  of  the  cylinder,  piston,  etc.,  is  vital  to  the  safety  of  the 


COOLING  AND  LUBRICATION  67 

engine.  A  steam  cylinder  lubricates  itself  by  condensation  of  steam 
on  the  cylinder  walls,  but  due  to  the  intense  heat  in  the  cylinder 
of  an  internal  combustion  engine,  and  due  to  the  high  piston  speed 
it  is  necessary  to  have  a  film  of  oil  between  the  piston  and  the 
cylinder  walls  at  all  times. 

Kind  of  Oil.  The  intense  heat  of  the  cylinder  will  tend  to 
evaporate  the  oil  and  cause  gumming,  therefore  an  oil  of  high 
heat  test  must  be  used.  As  this  is  limited  to  600°,  evaporation  of 
the  lubricant  cannot  be  eliminated  entirely;  therefore  a  thin  oil 
that  will  not  gum  upon  partial  evaporation  is  necessary.  Animal 
and  vegetable  oils  will  decompose  under  high  heat  and  cause  oxida- 
tion and  a  carbon  deposit  upon  the  cylinder,  not  to  mention  the 
possible  liberation  of  destructive  acid.  As  a  partial  combustion 
of  the  cylinder  lubricant  is  always  liable  to  take  place,  oil  must  be 
used  that  does  not  leave  any  solid  residue.  Only  special  grades 
of  mineral  oils  can  be  used.  These  are  designated  commercially 
as  "  gas  engine  cylinder  oils  "  and  come  in  various  grades  to  suit 
the  varying  conditions  of  speed,  load,  etc.  Oil  should  be  tested 
carefully  for  the  presence  of  acid.  A  good  body  and  low  internal 
friction  are  very  desirable. 

Two  distinct  methods  of  piston  and  cylinder  wall  lubrication  are 
employed:  (1)  splash  system;  (2)  mechanical  feed.  The  splash 
system  is  the  simpler  as  it  does  not  require  a  pump  for  distributing 
the  oil.  The  crank  case  is  closed  and  oil  is  maintained  in  the  case 
at  such  a  height  that  the  crank  or  a  small  lug  on  the  crank  will  dip 
into  the  oil  at  each  revolution,  throwing  the  oil  up  on  to  the  cylinder 
walls.  The  piston  spreads  the  oil  over  the  cylinder  wall  evenly  on 
the  up  stroke.  By  this  system  the  oil  supplied  to  the  cylinder  walls 
is  approximately  proportional  to  the  speed  of  the  engine.  At  the 
same  time  oil  is  splashed  on  to  all  of  the  bearings,  or  a  small  pump 
may  draw  oil  from  the  case  and  distribute  it  to  all  of  the  bearings, 
returning  it  to  the  case.  This  system  is  used  only  for  engines  of 
medium  and  low  horse-power. 

Lubricators.  The  mechanical  feed  appears  in  various  forms.  One 
is  shown  in  Figs.  44  and  45.  The  oil  is  fed  by  pump  or  mechanical 
lubricator  into  the  oil  duct  to  the  oil  ring  around  the  base  of 
the  cylinder,  Fig.  44.  At  each  stroke  the  lower  edge  of  the 


68 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


piston  dips  into  the  oil  in  the  oil  ring  and  oil  is  drawn  up  the 
cylinder  wall.  The  lubricator  is  shown  in  Fig.  45.  A  small  belt 
from  the  main  or  countershaft  drives  the  pulley  a.  This  revolves 
the  spindle  and  crank  l>,  b,  which  carries  the  loose  wire  c.  This 


FIG.  44.— Oil  Ring. 


FIG.  45. — Mechanical  Lubricator. 


wire  dips  into  the  oil  at  each  revolution  and  carries  a  small  amount 
to  the  wiper  d,,  from  which  the  oil  drips  to  the  passage  e.  This 
passage  connects  with  the  oil  duct  in  Fig.  44.  As  the  pulley  a  re- 
volves at  a  certain  relative  speed  to  the  main  shaft,  the  oil  supplied 
is  proportional  to  the  speed.  In  Fig.  45  the  central  bracket  which 
carries  the  wiper  d,  is  back  clear  of  the  path  of  spindle  and  crank 
b,  &,  as  they  revolve. 


CHAPTER  VIII 

GOVERNING  AND  INDICATOR  CAEDS 
Governing 

Internal  combustion  engine  governing  is  a  more  complex  propo- 
sition than  steam  engine  governing.  In  the  latter  case  the  medium 
of  power,  steam,  is  stable,  and  for  a  constant  pressure  a  given  gov- 
ernor position  will  always  give  the  same  cycle,  hence  constant  power. 
On  the  other  hand  the  working  fluid  in  an  internal  combustion 
engine  is  far  from  stable.  This  medium  consists  of  the  gas  re- 
sulting from  the  chemical  reaction  when  fuel  and  air  are  mixed  and 
ignited  in  the  engine  cylinder.  Thus  it  is  apparent  that  for  a  given 
fuel  the  stability  of  the  internal  combustion  engine  medium  de- 
pends upon  the  accuracy  and  variability  of  mixture,  degree  of 
stratification  of  the  charge,  and  variations  in  ignition.  The  per- 
fection of  agents  to  keep  these  variants  within  reasonable  limits  has 
made  possible  the  application  to  internal  combustion  engines  of 
governors  which  confine  the  speed  fluctuations  to  small  limits. 

As  in  the  steam  engine,  the  governor  must  fulfill  two  essentials, 
viz. :  It  must  automatically  control  the  speed  as  far  as  possible, 
and  it  must  be  isochronal  in  the  sense  that  under  varying  loads  it 
will  make  the  engine  perform  its  cycles  in  equal  times. 

The  mechanical  form  of  the  governor  varies  as  in  the  steam 
engine,  being  of  such  forms  as  the  fly-ball,  inertia,  and  vibrating 
types,  etc.  The  systems  employed  are: 

1.  The  hit  and  miss  system. 

2.  Throttling  the  mixture. 

3.  Varying  the  quality  of  the  mixture. 

4.  Varying  the  point  of  ignition. 

5.  Throttling  the  exhaust. 

6.  Combination  systems. 

Governing  by  the  Hit  and  Miss  System.     In  one  of  its  forms  this 
was  the  earliest  system  employed  extensively  to  regulate  internal 
combustion  engine  speed.    It  effects  this  regulation  by  omitting  an 
6 


70  INTERNAL  COMBUSTION  ENGINE  MANUAL 

explosion  when  the  speed  exceeds  that  desired.  When  running  at 
the  required  speed  the  cycles  follow  each  other  at  equal  intervals; 
if  anything  disturbs  this  equilibrium  so  as  to  increase  the  speed  the 
governor  acts  and  prevents  an  explosion  (causes  a  "miss")  on  the 
following  cycle.  This  miss  reduces  the  speed  and  the  governor  acts 
in  the  opposite  direction,  causing  the  explosions  to  recur.  The 
greater  the  excess  speed,  the  greater  will  be  the  proportion  of 
"misses"  to  "hits"  until  equilibrium  is  again  restored.  There 
are  three  varieties  to  this  system: 

1.  Keeping  the  fuel  valve  closed  so  that  only  air  is  drawn  into 
the  cylinder  during  the  miss  cycle. 

2.  Keeping  the  inlet  valve  closed,  thus  preventing  admission  of 
both  air  and  fuel. 

3.  Keeping  the  exhaust  valve  open,  thus  destroying  suction  action 
on  the  admission  stroke  of  the  cycle. 

The  mechanical  operation  of  the  first  two  methods  is  the  same, 
the  only  difference  being  that  in  the  first  case  the  governor  acts 
upon  the  fuel  valve  and  in  the  second  case  it  acts  upon  the  admis- 
sion valve.  Fig.  46,  called  the  pick-blade  governor,  illustrates  this 
method.  A  is  the  fuel  or  admission  valve.  B  is  a  bell  crank  lever 
which  actuates  the  valve,  opening  and  shutting  it  during  the  regular 
cycle.  This  bell  crank  lever  is  in  turn  actuated  by  the  cam  C  on 
the  countershaft.  The  pick-blade  D  acts  as  the  push  rod  between 
the  valve  stem  and  the  lever  B  during  a  regular  cycle.  This  pick- 
blade  is  connected  by  rod  E  and  bell  crank  F  to  a  collar  G  on  the 
governor  H.  The  governor  is  run  by  the  main  or  countershaft  so 
that  its  speed  is  proportional  to  that  of  the  engine.  When  the  pick- 
blade  engages  the  valve  stem  it  is  in  position  for  running  at  the  de- 
sired speed.  If  this  speed  is  exceeded,  the  governor  balls  fly  out- 
ward, raising  the  collar  G.  This  causes  the  pick-blade  to  move  to 
the  right  as  shown  and  disengage  the  valve  stem  entirely.  During 
the  next  cycle  and  until  the  speed  is  reduced  to  the  normal,  the 
pick-blade  does  not  engage  the  valve  stem  and  the  valve  does  not 
lift.  This  operation  causes  misses.  When  the  speed  is  reduced  the 
required  amount,  the  balls  of  the  governor  assume  their  original 
position,  the  pick-blade  again  engages  the  valve  stem,  and  the 
original  conditions  are  resumed. 


GOVERNING  AND  INDICATOR  CARDS 


71 


The  system  of  governing  by  keeping  the  exhaust  valve  open  is 
often  applied  to  engines  that  have  an  automatic  spring  loaded  ad- 
mission valve.  By  applying  the  governor  to  the  exhaust  valve  this 
can  be  kept  open  when  the  speed  exceeds  that  desired,  and  with  this 


FIG.  46. — Pick-Blade  Governor.    Governing  by  the  "  Hit  and  Miss  " 

System. 

open  no  vacuum  is  created  on  the  suction  stroke  and  hence  no  fresh 
charge  is  drawn  in.  The  result  is  a  miss  on  the  following  cycle. 
When  normal  speed  is  again  reached,  the  exhaust  valve  is  released 
and  functions  as  originally. 

It  is  obvious  that  this  system  is  open  to  many  objections.  In  a 
four  cycle  engine  the  omission  of  a  working  cycle  will  cause  an 
appreciable  variation  of  the  speed  even  with  a  large  fly-wheel,  and  if 


72  INTERNAL  COMBUSTION  ENGINE  MANUAL 

the  load  is  suddenly  increased  just  after  the  miss  cycle,  this  reduc- 
tion becomes  objectionably  large.  After  the  idle  cycle,  the  first 
impulse  is  stronger  than  normal  due  to  the  cylinder  being  well 
scavenged  during  the  miss  cycle.  An  engine  employing  the  hit  and 
miss  system  requires  a  very  heavy  fly-wheel  to  produce  a  reasonably 
uniform  angular  velocity  in  the  crank  shaft.  This  system  is  unsuit- 
able for  work  requiring  close  regulation  of  speed,  such  as  electric 
lighting,  etc.  Its  advantages  as  a  system  are  its  mechanical  sim- 
plicity, and  its  ability  to  run  on  the  economical  quality  of  mixture 
without  variation. 

Governing  by  Throttling  the  Mixture.  A  more  efficient  system 
of  governing  than  the  foregoing  is  that  of  throttling  the  normal 
mixture  so  that  a  smaller  quantity  of  the  charge  is  drawn  into  the 
cylinder,  but  the  proportions  of  that  charge  are  unchanged.  The 
governor  operates  the  main  throttle  which  is  generally  placed  in  the 
admission  line  between  the  carbureter  and  the  engine.  The  ad- 
vantages of  this  system  are  that  the  engine  can  work  on  a  constant 
mixture  and  receives  an  impulse  every  cycle.  The  pressure  in  the 
cylinder  is  reduced  by  throttling,  due  to  both  reduced  fuel  supply, 
and  to  consequent  decreased  compression.  By  keeping  a  constant 
quality  the  danger  of  ignition  failure  is  reduced. 

When  this  system  is  used  the  engine  is  designed  for  a  very  high 
compression  at  full  power  so  that  with  a  reduced  amount  of  fuel 
the  remaining  compression  will  enable  a  good  thermal  efficiency  to 
be  attained.  The  advantages  of  this  system  has  caused  a  tendency 
for  its  general  adoption  for  many  uses. 

Governing  by  Varying  the  Quality  of  the  Mixture,  For  a  given 
quantity  of  mixture  the  initial  pressure  obtained  will  vary  with 
the  proportion  of  fuel  and  air  in  the  mixture.  This  is  the  principle 
of  variable  quality  governing.  The  governor  may  act  upon  the  fuel 
valve,  varying  the  amount  of  fuel  per  cycle  while  the  amount  of  air 
remains  constant,  or  may  act  upon  the  air  valve,  varying  the  amount 
of  air  per  cycle,  the  fuel  valve  being  automatic.  The  result  in 
either  case  is  to  impoverish  the  mixture  when  the  speed  exceeds  that 
for  which  the  governor  is  set.  It  has  the  advantage  that,  although 
the  total  charge  of  fuel  and  air  may  vary  in  quality,  the  quantity 


GOVERNING  AND  INDICATOR  CARDS  73 

admitted  each  cycle  is  constant,  therefore  the  compression  is  the 
same  for  varying  loads.  Theoretically  the  result  should  be  equal 
thermal  efficiencies  for  all  loads,  but  practically  the  fuel  consump- 
tion rapidly  increases  as  the  load  decreases. 

The  reason  for  this  decrease  of  thermal  efficiency  with  the  load 
under  this  system  of  governing  is  that  as  the  mixture  becomes  rarer, 
ignition  becomes  more  difficult  and  combustion  much  slower,  result- 
ing in  greater  heat  losses  to  the  cylinder  walls.  If  carried  too  far 
the  mixture  may  become  so  rare  that  it  cannot  be  ignited. 

Governing  by  Varying  the  Point  of  Ignition.  The  ignition  sys- 
tems of  nearly  all  internal  combustion  engines  are  so  fitted  that  the 
point  in  the  engine  stroke  at  which  ignition  takes  place  may  be 
varied.  The  electrical  systems  particularly  lend  themselves  to  this 
form  of  regulation.  Thus  the  charge  may  be  ignited  before  the 
piston  reaches  the  end  of  the  compression  stroke  ("advanced 
spark"),  at  the  end  of  the  compression  stroke  when  the  compression 
is  a  maximum,  or  on  the  expansion  stroke  beyond  the  dead  center 
(" retarded  spark").  It  is  evident  that  the  maximum  impulse  is 
obtained  if  combustion  takes  place  when  the  compression  pres- 
sure is  a  maximum.  If  ignition  takes  place  after  the  piston  has 
passed  the  dead  center  and  started  on  the  combustion  stroke,  then 
the  compression  being  less  than  maximum,  the  power  obtained  is 
less  than  full  power.  If  the  charge  is  ignited  and  combustion  takes 
place  before  the  piston  has  passed  the  compression  stroke  dead 
center,  it  is  evident  that  the  piston  will  be  driven  backwards  ("  back 
fire")  unless  the  fly-wheel  inertia  is  sufficient  to  carry  the  piston 
over  the  dead  center. 

This  system  is  used  extensively  in  marine  engines  as  well  as  in 
motor  vehicles.  Its  use  facilitates  hand  starting  by  preventing 
"  back  firing."  To  start,  the  ignition  is  retarded  well  past  the  dead 
center.  After  the  engine  is  running  the  spark  is  advanced  until 
ignition  takes  place  a  little  ahead  of  the  dead  center.  The  reason 
for  this  is  that,  combustion  not  being  instantaneous,  if  the  charge 
is  ignited  at  the  proper  point  before  the  piston  reaches  the  dead 
center,  the  maximum  pressure  of  combustion  will  occur  at  the  end 
of  the  stroke,  and  the  expansion  will  thus  be  a  maximum. 

The  proper  ignition  point  is  found  as  follows :     Advance  the 


74  INTERNAL  COMBUSTION  ENGINE  MANUAL 

spark  until  a  distinct  " knock"  is  heard.  Then  retard  the  spark 
until  this  knock  just  disappears. 

Governing  by  Throttling  the  Exhaust,  If  the  exhaust  be  throt- 
tled it  will  produce  a  braking  effect  or  back  pressure  during  the 
exhaust  stroke.  This  effect  is  particularly  noticeable  in  a  single 
cylinder  engine.  Another  effect  of  throttling  the  exhaust  is  to 
leave  some  of  the  products  of  combustion  in  the  cylinder  which 
prevents  a  full  charge  being  drawn  in  on  the  suction  stroke.  More- 
over, the  reduced  charge  is  diluted  by  the  exhaust  gases  present. 
This  system  being  highly  inefficient  is  little  used. 

Combination  Systems  of  Governing.  Although  not  general,  com- 
bination systems  are  sometimes  used.  Some  American  Crossley 
engines  govern  by  the  variable  quantity  or  quality  method  at  high 
loads  and  by  the  hit  and  miss  system  at  low  loads.  Some  engines 
govern  by  the  variable  quantity  method  at  high  loads  and  by  the 
variable  quality  method  at  low  loads,  and  vice  versa.  A  thermally 
correct  method  is  that  advanced  by  Letombe.  This  consists  of  in- 
creasing the  time  of  opening  of  the  inlet  valve,  but  decreasing  the 
lift  of  the  fuel  valve  as  the  load  decreases.  In  a  sense  this  is 
quantity  regulation,  but  the  increased  opening  of  the  inlet  valve  in- 
creases the  total  charge,  and  thus  the  leaner  mixtures  are  more 
highly  compressed  than  the  richer  mixtures  that  are  used  at  the 
higher  loads.  Attempts  have  been  made  to  vary  the  compression 
space  so  that  the  compression  can  be  made  constant  for  all  loads, 
but  no  practical  method  embodying  this  principle  has  been  devised. 

Indicator  Cards 

The  theoretical  four  cycle  engine  indicator  card  with  variations 
is  shown  in  Figs.  47  to  52..  Fig.  47  illustrates  a  theoretically  per- 
fect card.  All  the  strokes  and  events  in  the  cycle  are  marked  and 
starting  at  any  point  the  cycle  can  be  easily  traced.  It  is  apparent 
when  tracing  the  cycle  that  the  lower  loop  is  traced  in  the  opposite 
direction  to  the  upper  loop.  This  indicates  a  loss  of  work  and  the 
work  represented  by  the  lower  loop  must  be  subtracted  from  that 
represented  by  the  upper  loop  to  get  the  net  work  of  the  cycle.  In 


GOVERNING  AND  INDICATOR  CARDS  75 

cards  48  to  50  the  suction  and  exhaust  strokes  are  omitted  for 
simplicity  of  discussion. 


FIG.  47. — Normal  Indicator  Card. 


Fig.  48  shows  the  effect  of  throttling  the  normal  charge.  A  num- 
ber of  cards  are  superposed  to  illustrate  the  point  that  as  the  charge 
is  throttled  the  card  becomes  smaller,  showing  a  decrease  in  total 


FIG.  48. — Effect  of  Throttling  the  Normal  Charge. 

work.  Throttling  decreases  the  amount  of  mixture  that  is  drawn  in 
each  cycle.  As  the  charge  is  reduced,  the  compression  space  being 
the  same,  the  compression  pressure  is  lowered,  and  as  a  direct  result 
of  the  reduced  pressure  combustion  is  slower.  These  points  are 
indicated  in  the  card  by  the  lowered  compression  line  and  the 
sloping  combustion  line  respectively. 


76  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Several  cards  are  superposed  in  Fig.  49  to  show  the  effect  of  re- 
tarding the  ignition.  If  ignition  takes  place  after  the  piston  passes 
the  dead  center  this  is  indicated  on  the  card  by  the  combustion  line 
returning  along  the  compression  line  until  the  point  of  ignition  is 


FIG.  49. — Effect  of  Retarding  the  Ignition. 

reached.  The  later  the  ignition,  the  lower  will  be  the  compression 
at  the  point  of  ignition,,  therefore  the  combustion  will  be  slower  and 
the  combustion  line  will  be  lower. 

Fig.  50  is  a  card  from  an  engine  that  has  the  spark  advanced  too 
far,  in  other  words  the  ignition  is  too  early.  Ignition  in  this  case 
takes  place  before  the  end  of  the  compression  stroke,  the  maximum 


FIG.  50. — Ignition  too  Early. 

pressure  is  attained  before  this  stroke  is  completed,  and  the  result 
is  a  loop  in  the  upper  part  of  the  card,  which  loop  being  traced  in 
the  reverse  direction  to  the  general  direction  of  the  cycle  represents 
a  loss  of  work. 

Fig.  51  is  a  card  taken  from  an  engine  with  a  faulty  exhaust. 
This  fault  may  arise  from  a  clogged  exhaust,  the  exhaust  valve  or 
passages  may  be  designed  too  small,  the  exhaust  valve  may  be  in- 
correctly timed,  the  exhaust  passage  may  be  so  long  as  to  create  a 


GOVERNING  AND  INDICATOR  CARDS 


77 


back  pressure  or  may  have  sharp  bends  or  turns  in  it.  In  any  case 
any  cause  that  would  interrupt  the  exhaust  enough  to  create  a  back 
pressure  will  be  indicated  on  the  card  by  a  rise  in  the  exhaust  line. 


FIG.  51. — Faulty  Exhaust. 


FIG.  52. — Faulty  Admission  or  Suction. 

When  the  suction  line  falls  below  the  atmospheric  as  in  Fig.  52, 
this  indicates  that  the  admission  is  partly  choked.  This  may  be 
caused  by  too  small  an  admission  valve,  admission  passages  too  small 
or  too  many  bends  in  the  passage,  inlet  choked,  or  not  enough  lift 
to  admission  valve;  if  a  spring  loaded  admission  valve  then  the 
spring  may  be  too  strong,  thus  decreasing  the  lift. 


78 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


Fig.  53  is  an  indicator  card  from  a  two  cycle  engine,  the  upper 
card  being  taken  from  the  cylinder  of  the  engine  and  the  lower  card 
from  the  crank  case  or  compressor.  These  are  traced  in  opposite 
directions  so  that  the  work  indicated  is  the  difference  between  the 
works  represented  by  the  two  cards.  The  upper  card  is  traced  in 
the  forward  direction. 

From  the  foregoing  examples  it  can  be  readily  seen  how  important 
is  the  information  that  can  be  gained  from  good  indicator  cards. 


f  Ignition,  a  Expansion,  b  Exhaust,  2  Crank  Case  Card. 
FIG.  53. — Two  Cycle  Engine  Card. 

All  faults  of  internal  working  may  be  obtained  from  well  taken 
cards.  They  give  data  on  performance,  and  valve  settings,  etc.,  can 
be  checked  by  them.  Manufacturers,  however,  are  more  interested 
in  the  brake  horse-power  than  in  the  indicated  horse-power  and  all 
factory  tests  are  made  for  the  former. 

Indicators.  The  Manograph.  The  power  of  an  internal  com- 
bustion engine  is  measured  in  a  manner  similar  to  that  employed  in 
measuring  the  power  of  a  steam  engine.  That  is,  indicator  cards  are 
taken  to  obtain  the  mean  effective  pressure  acting,  and  this,  with  the 
number  of  revolutions  and  the  engine  dimensions,  gives  the  neces- 


GOVERNING  AND  INDICATOR  CARDS 


79 


sary  data  for  use  in  the  horse-power  formula.  For  slow  moving, 
heavy  duty  engines,  indicators,  similar  to  steam  engine  indicators, 
may  be  used.  These  indicators  have  external  springs.  However, 
they  are  impractical  for  the  high-speed  engines  because  of  the 
inertia  of  the  parts,  the  liability  of  the  cords  and  other  flexible 
parts  to  stretch,  and  the  frequency  with  which  the  springs  break. 
Indicator  cards  for  high-speed  engines  are  taken  by  an  ingenious 
device  called  the  manograph.  This  indicator  overcomes  the  in- 
herent difficulties  of  the  ordinary  piston  type  of  indicator  by  substi- 
tuting a  beam  of  light  for  the  pencil  of  the  ordinary  indicator  and 
this  beam  traces  a  card  on"  a  ground  glass  screen  or  a  photographic 


FIG.  54. — The  Manograph,  Cross  Section. 

plate.  The  former  is  used  for  a  casual  inspection  of  the  engine's 
performance  and  the  latter  is  used  when  a  permanent  record  is 
desired. 

The  manograph,  which  can  be  seen  in  the  laboratory,  consists  of 
a  light-tight  box  mounted  on  a  tripod.  At  one  end  of  this  box, 
Figs.  54  and  55,  a  mirror  N  is  so  mounted  that  it  is  capable  of  rota- 
tion about  two  axes  at  right  angles  to  each  other.  An  acetylene 
burner  G  on  one  side  of  the  box,  shining  through  a  diaphragm,  re- 
flects a  beam  of  light  through  the  prism  H  to  the  mirror  N.  This 
beam  is  again  reflected  from  the  mirror  N  on  to  the  screen  or  plate 
D.  The  mirror  N  is  given  two  motions,  one  in  proportion  to  the 
piston  motion,  and  the  other  at  right  angles  to  the  first  in  propor- 
tion to  the  pressure  on  the  piston  at  any  simultaneous  piston  position. 
As  the  mirror  moves  in  two  directions  the  beam  of  light  will  follow 


80 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


a  path  which  is  compounded  from  two  rectangular  co-ordinates,  one 
proportional  to  the  piston  position,  and  the  other  proportional  to 
the  simultaneous  piston  pressure.  In  other  words  the  beam  will 
trace  a  card  on  the  screen  similar  to  a  card  obtained  by  an  ordinary 
indicator,  but,  since  the  moving  part  in  the  manograph  is  the  beam 
of  light  which  has  no  inertia,  the  inaccuracies,  due  to  inertia  of 
parts,  etc.,  are  eliminated. 


FIG.  55. — Details  of  Manograph. 

Motion  proportional  to  pressure  is  given  the  oscillating  mirror 
as  follows :  The  mirror  is  mounted  on  springs,  Fig.  55,  which  tend 
to  keep  it  parallel  to  the  screen.  The  tube  T  communicates  with 
the  engine  cylinder  and  allows  the  cylinder  pressure  to  act  on  the 
diaphragm  M.  This  diaphragm  is  connected  with  the  mirror  N  by  a 
pin  offset  from  the  mirror  center.  It  is  obvious  that  the  mirror 
will  be  rotated  by  this  pin  an  amount  proportional  to  the  pressure 
on  the  diaphragm,  which  is  the  cylinder  pressure.  The  tube  T  can 
communicate  with  the  different  cylinders  on  a  multicylinder  engine 
by  means  of  a  multiway  cock. 

Motion  proportional  to  the  piston  travel  is  given  the  mirror  N  as 
follows:  the  flexible  shaft  R  (Fig.  56)  is  connected  to  the  crank 
shaft  center  and  rotates  with  the  shaft.  By  means  of  the  gear  L 


GOVERNING  AND  INDICATOR  CARDS 


81 


and  a  pin,  which  is  90°  on  the  mirror  from  the  other  pin,  motion 
proportional  to  the  piston  travel  is  imparted  to  the  mirror,  for  the 
mirror  receives  one  complete  oscillation  each  revolution  of  the  engine. 


FIG.  56. — The  Manograph. 


FIG.  57. — The  Manograph. 

The  angular  motion  of  the  mirror  is  very  small.  The  thumb 
screw  F  is  for  the  purpose  of  establishing  synchronism  between  the 
engine  crank  and  the  small  manograph  crank  that  actuates  the  pin  c. 

A  manograph  is  installed  in  the  laboratory  on  the  Mietz  and 
Weiss  engine. 


CHAPTER  IX 

EFFICIENCY,  MANAGEMENT,  OPERATION,  DEFECTS 
AND  REMEDIES 

Efficiency 

The  efficiency  of  an  engine  is  the  ratio  of  the  heat  converted  into 
mechanical  work  to  the  total  heat  which  enters  the  engine.  The  effi- 
ciency of  a  perfect  heat  engine  therefore  depends  upon  two  things 
only,  viz. :  the  initial  and  final  temperature  of  the  medium,  or  the 
temperatures  of  source  and  refrigerator.  The  greater  this  range  of 
temperature,  the  greater  will  be  this  efficiency.  The  equation  for 

the  efficiency  of  a  perfect  heat  engine  is  E=J^-i ,  where  E  is  the 

efficiency,  ^  the  initial  temperature  and  t2  the  final  temperature. 

Although  illogical  to  employ  this  formula,  which  is  applicable  to 
the  perfect  heat  engine  only,  to  compare  the  steam  and  internal 
combustion  engines,  the  information  obtained  is  interesting ;  for  ex- 
ample a  steam  engine  working  between  250  pounds  absolute  and 
24  inch  vacuum  or  3  pounds  absolute,  and  an  internal  combustion 
engine  working  between  2000°  F.  and  600°  F.  are  taken.  In  the 
case  of  the  steam  engine  ^=478°  absolute,  and  £2  =  334°  absolute, 
and  E=.30  or  30  per  cent.  In  the  case  of  the  internal  combustion 
engine  ^  =  1366°  absolute,  and  t>  =  589°  absolute,  and  #=.57  or 
57  per  cent.  This  shows  that  theoretically  the  internal  combustion 
engine  can  attain  about  twice  the  thermal  efficiency  of  the  steam 
engine  due  to  the  increased  range  of  working  temperatures. 

It  can  be  shown  that  the  theoretical  efficiency  depends  upon  the 
degree  of  compression  only,  and  is  independent  of  the  maximum 
temperature  if  expansion  is  carried  to  the  atmospheric  pressure. 

Thus  E  =  1  — —  where  t  is  the  temperature  before  compression  and 
ic  is  the  temperature  after  compression.  E  therefore  depends  upon 
the  ratio  j-  .  But—  =  f-^M  "^  where  p  is  the  pressure  before 


EFFICIENCY,  MANAGEMENT,  OPERATION,  ETC.  83 

compression  and  pc  is  the  pressure  after  compression  and  A,  is  the  ratio 
of  the  specific  heat  at  constant  volume  to  the  specific  heat  at  constant 

pressure.    Now  the  value  of——  and  therefore  of  (  -£-£-  J  "~A~  depends 

upon  the  compression  only,  therefore  E  also  depends  upon  the  com- 
pression only. 

Although  apparently  paradoxical,  this  is  an  important  point.  If 
an  engine  receives  all  of  its  heat  at  one  pressure  and  rejects  all  of 
its  waste  heat  at  another,  and  the  reduction  in  pressure  is  utilized 
to  do  work  by  expansion,  the  efficiency  is  constant  regardless  of  the 
maximum  temperature.  The  proportion  of  heat  converted  into 
work  is  not  changed  by  increasing  the  temperature  before  com- 
pression. 

If  expansion  is  not  carried  to  the  atmospheric  pressure,  and  this 
is  rare  in  practice,  the  above  is  not  strictly  true ;  compression  is  still 
the  governing  factor,  but  heating  before  compression  slightly  in- 
creases the  theoretical  efficiency. 

When  the  practical  efficiency  is  considered  heating  before  com- 
pression decreases  the  efficiency  by  increasing  the  loss  of  heat  by 
radiation.  Ordinarily  the  most  efficient  temperature  for  the  en- 
tering mixture  seems  to  be  between  80°  F.  and  85°  F.  Cooling 
water  is  generally  carried  near  the  boiling  point,  say  about  180°  F. 
This  is  sufficiently  low  to  prevent  deformation  of  the  cylinders. 

To  Start  and  Stop  a  Motor.  Small  motors  may  be  started  by 
hand  by  giving  a  few  turns  to  the  fly-wheel  or  to  a  crank  fitted  to 
the  crank  shaft,  but  the  larger  engines  require  an  auxiliary  starting 
mechanism.  Some  engines,  such  as  the  Standard,  are  fitted  so  that 
they  may  be  run  by  compressed  air  for  a  few  revolutions  until  the 
first  explosion  is  obtained.  Another  method  is  to  introduce  a  charge 
of  mixture  into  a  cylinder  by  a  pump,  and  then  to  fire  this  charge  by 
the  igniter  or  a  detonator.  When  using  this  latter  method,  care 
must  be  taken  that  the  piston  is  on  the  expansion  stroke,  for,  if  it 
is  on  the  compression  stroke,  a  back-fire  will  result  and  the  engine 
will  start  in  the  reverse  direction;  this  causes  undue  stress  on  the 
parts  and  may  even  fracture  the  main  or  crank  shaft. 

In  most  engines  the  point  of  ignition  is  capable  of  adjustment. 
In  this  case  retard  the  spark  so  that  ignition  will  occur  after  the 


84  INTERNAL  COMBUSTION  ENGINE  MANUAL 

crank  passes  the  dead  center.  See  that  the  ignition  circuit,  oiling 
gear  and  cooling  water  are  in  order  and  turned  on.  Open  the  throt- 
tle, fuel  valve  to  carbureter  if  installed,  prime  the  cylinder  and  open 
the  relief  cocks  on  the  cylinders  if  necessary.  Give  the  engine  a  few 
turns  by  the  fly-wheel,  if  small,  or  the  starting  device,  if  large,  and, 
if  everything  is  in  order,  the  engine  will  start.  Opening  the  relief 
cocks  relieves  the  compression  and  makes  cranking  easy;  on  the 
other  hand,  relieving  the  compression  makes  ignition  more  difficult. 
The  behavior  of  the  engine  at  hand  will  govern  this  point.  After 
the  engine  is  started,  adjust  the  ignition  to  the  proper  lead,  close 
the  relief  cocks  if  open,  see  that  the  oil  and  water  are  working 
properly,  and  adjust  the  mixture  if  necessary.  These  general  in- 
structions may  be  modified  for  different  types  of  engines.  If  an 
engine  is  to  stop  but  a  few  moments,  the  ignition  circuit  may  be 
broken,  if  of  the  jump  spark  type  with  battery  and  coil.  The  few 
revolutions  due  to  inertia  after  the  spark  is  cut  off  will  leave  the 
cylinders  charged  with  the  mixture.  By  again  "closing  the  ignition 
circuit  a  spark  will  jump  in  the  cylinder  that  has  its  piston  in  the 
firing  position,  and,  if  the  mixture  is  still  in  combustible  form,  the 
engine  will  start  without  cranking.  This  is  called  "starting  on 
spark." 

To  stop  the  engine,  close  the  throttle,  break  the  ignition  circuit, 
and  close  the  fuel  valve.  If  exposed  to  freezing  weather,  drain  engine 
jackets  and  connecting  pipes.  Although  it  has  been  recommended 
that  the  oil  supply  be  shut  off  before  the  engine  is  stopped  in  order 
that  the  surplus  oil  may  be  carried  out  with  the  exhaust,  the  author 
is  not  in  agreement.  If  the  oil  supply  is  properly  regulated,  there 
will  not  be  enough  surplus  to  cause  serious  clogging  in  the  cylinder 
or  valves,  whereas  the  serious  results  that  might  occur  if  the  engine 
were  started  without  turning  on  the  oil  supply  (as  might  easily 
happen  if  other  than  the  regular  hand  started  the  engine)  are 
obvious.  Wrecks  from  this  cause  are  not  infrequent.  In  modern 
practice,  especially  where  the  splash  system  is  used,  the  oil  supply 
is  left  turned  on  at  all  times.  This  does  not  apply  to  heavy  duty 
motors  having  special  feed  systems. 

Failure  to  Start.  Should  the  motor  fail  to  start,  the  trouble  can 
only  be  found  by  a  man  conversant  with  the  interrelation  of  the 


EFFICIENCY,  MANAGEMENT,  OPERATION,  ETC.  85 

parts  of  the  machine  and  their  relative  functions,  and  "trouble 
hunting"  resolves  itself  into  an  investigation  of  the  different  in- 
tegral systems  of  the  motor.  Of  course  many  causes  of  non-start- 
ing are  apparent  from  the  behavior  of  the  machine,  and  an  ex- 
perienced hand  will  generally  have  little  trouble  in  finding  the 
defect.  However,  occasionally  a  defect  will  baffle  even  an  expert 
until  he  has  thoroughly  overhauled  and  analyzed  the  motor. 
When  investigating  non-starting,  divide  the  machine  as  follows : 

1.  Ignition  system. 

2.  Fuel  system. 

Non-Starting  Due  to  Faulty  Ignition 

First  look  to  the  spark.  It  may  be  too  feeble  to  ignite  the  mix- 
ture or  may  not  occur  at  all.  In  this  case  first  test  the  battery.  If 
this  is  found  in  good  condition,  test  the  line  up  to  the  plug  for 
broken  wires,  short  circuits  or  poor  contacts.  Finally  look  at  the 
plug.  It  may  be  too  foul  for  the  spark  to  bridge,  the  points  may 
be  too  far  apart,  or  the  insulation  may  be  defective. 

If  a  good  spark  is  present  at  the  plug,  then  it  may  be  taking  place 
at  the  wrong  part  of  the  cycle,  due  to  the  timer  being  out  of  adjust- 
ment. This  discrepancy  is  made  good  by  so  adjusting  the  timer 
that  the  spark  will  occur  at  or  just  beyond  the  end  of  the  compres- 
sion stroke.  If  the  spark  is  strong  enough  for  ignition  and  is 
properly  timed,  then  the  trouble  will  be  found  under  the  second  head. 

Non-Starting  Due  to  Fuel  Supply 

The  tank  may  be  empty  or  the  fuel  valve  closed.  Although  this 
sounds  childish,  many  operators  have  wasted  much  valuable  time 
trying  to  start  under  these  conditions.  The  feed  pipe  may  be 
clogged.  Often  waste  or  other  foreign  matter  find  their  way  into 
the  feed  pipes  through  the  tank.  The  throttle  or  the  air  valve  may 
be  stuck.  Defective  adjustment  of  the  air  valve  may  result  in  a 
non-combustible  mixture.  The  carbureter  may  be  out  of  order.  A 
leaky  needle  valve,  resulting  in  a  flooded  carbureter,  is  a  frequent 
source  of  trouble.  The  compression  may  be  defective,  due  to  leaky 
or  broken  piston  rings  or  valves.  This  is  evidenced  by  the  small 
7 


86  INTERNAL  COMBUSTION  ENGINE  MANUAL 

resistance  encountered  when  cranking  the  engine.  A  broken  valve 
stem  or  loose  valve  cam,  which  does  not  show  at  once,  may  cause  a 
valve  to  become  inoperative.  In  a  neAV  installation  the  tank  may  be 
too  low  to  supply  a  gravity  feed,  or  the  lead  of  feed  pipe  may  be  bad. 

Common  Defects  and  their  Causes 

Back-Firing.  This,  one  of  the  commonest  of  the  defects,  con- 
sists of  explosions  in  the  passages  outside  of  the  cylinder.  They 
may  be  located  in  the  exhaust  pipe  or  passages,  or  in  the  inlet  passage 
between  the  carbureter  and  inlet  valve.  In  the  case  of  exhaust 
passage  explosions,  the  ignition  may  be  too  late.  Combustion  is  in- 
complete when  the  exhaust  valve  opens,  and  some  of  the  unburnt 
charge  finds  its  way  to  the  exhaust  passage  where  it  explodes.  When 
governing  by  the  hit  and  miss  system  the  charge  of  a  miss  cycle  may 
explode  in  the  exhaust  passage  when  the  hot  exhaust  of  the  next 
exploded  charge  comes  in  contact  with  it.  A  mixture  which  burns 
so  slowly  that  combustion  is  incomplete  when  the  exhaust  valve 
opens  will  have  the  same  effect  as  late  ignition. 

Back-firing  in  the  admission  passage  is  more  perplexing.  A  leaky, 
broken  or  badly  timed  admission  valve  may  transmit  the  combustion 
within  the  cylinder  to  the  fresh  charge  in  the  admission  passage, 
causing  a  back-fire  there.  Another,  and  very  common,  cause  for 
this  form  of  back-firing  is  a  too  thin  mixture.  A  very  lean  mixture 
burns  slowly,  and  the  combustion  may  continue  throughout  the  ex- 
haust stroke  until  the  inlet  valve  opens,  thus  exploding  the  mixture 
in  the  inlet  passage.  A  very  rich  mixture  might  act  in  the  same 
manner,  but  it  is  more  likely  to  cause  a  back-fire  in  the  exhaust 
passage.  A  loose  valve  cam  may  cause  back-firing  by  timing  an 
admission  or  exhaust  valve  improperly. 

Misfiring.  There  are  two  distinct  classes  of  misfiring,  continuous 
and  intermittent.  Continuous  misfiring  of  one  cylinder  of  a 
multiple  cylinder  engine  is  a  simple  problem.  The  trouble  is  almost 
certain  to  be  in  the  ignition  system,  because  the  operation  of  the 
other  cylinders  indicates  that  the  fuel  supply  is  operative  as  far  as 
the  admission  valve  of  the  defective  cylinder,  and  were  trouble 
located  in  the  valves  of  the  defective  cylinder  it  would  generally  be 


EKFICTKXCY.   MANAGEMENT,  OPERATION,  ETC.  87 

accompanied  by  back-firing.  If  the  valves  are  found  to  be  function- 
ing correctly  then  the  ignition  system  must  be  overhauled.  The 
system  must  be  operative  as  far  as  the  coil  because  if  it  were  de- 
fective in  the  battery  or  primary  line  to  the  coil  all  the  cylinders 
would  fail  to  fire.  Among  the  ignition  defects  that  might  cause 
misfiring  in  one  cylinder  are  foul  or  defective  plug,  broken  wire  or 
bad  contacts,  or  improperly  adjusted  coil  vibrator.  These  are  all 
easily  found  by  simple  electrical  tests. 

Intermittent  misfiring  may  be  caused  by  improper  mixture,  weak 
battery,  poorly  adjusted  coil,  broken  wires  or  connections  that  are 
in  contact  intermittently  due  to  the  vibration  of  the  engine,  dirty 
sparking  device,  admission  valve,  if  automatic,  not  working  freely, 
exhaust  valve  not  closing  every  cycle,  leaky  valves  and  poor  com- 
pression, or  water  in  the  gasoline. 

Carbureter  explosions  have  the  same  origin  as  admission  pipe 
back-firing. 

Muffler  explosions  have  the  same  origin  as  exhaust  pipe  back- 
firing. 

Weak  explosions  are  due  to  late  ignition,  weak  battery,  poor 
quality  of  the  mixture,  insufficient  compression,  or  loss  of  compres- 
sion due  to  leaky  or  broken  piston  rings  or  valves.  Overheating 
may  give  weak  explosions  and  attendant  loss  of  power  due  to  the 
dissociation  of  the  mixture  to  its  elements. 

Overheating  may  be  occasioned  by  one  of  three  defects,  excess 
friction  due  to  poor  adjustment  of  bearings,  etc.,  defective  circu- 
lating water  supply,  or  failure  of  the  lubricating  system.  The  water 
supply  may  fail  totally  or  partially  due  to  pump  breakdown,  clogging 
of  the  pipes,  closed  valve  in  the  line,  or  sediment  on  the  cylinder 
walls.  When  the  water  supply  fails  the  temperature  quickly  rises 
high  enough  to  burn  the  oil  and  damage  ensues,  the  piston  rings 
and  cylinder  walls  wear  and  the  piston  will  ultimately  seize.  Failure 
of  the  oil  supply  if  not  discovered  early  results  in  the  same  serious 
trouble.  Serious  overheating  is  attended  by  loss  of  power  and  this 


88  INTERNAL  COMBUSTION  ENGINE  MANUAL 

is  an  early  indication  that  should  be  a  warning  signal  to  an  ex- 
perienced man. 

Knocking  may  be  due  to  mechanical  trouble  such  as  loose  bear- 
ings, etc.,  or  to  explosive  defects.  Under  the  latter  head  there  are 
two  recognized  classes  of  knocks,  a  "  gas  knock "  and  a  "  spark 
knock."  A  gas  knock  is  caused  by  too  rich  a  mixture  or  by  opening 
the  throttle  too  quickly.  It  is  an  infrequent  phenomenon.  A 
spark  knock  is  caused  by  advancing  the  spark  too  far.  A  slight 
pre-ignition  occurs,  and  though  it  is  not  early  enough  to  cause  re- 
versal of  the  engine  rotation,  it  puts  undue  stress  on  the  parts  and 
causes  a  tinny  thump.  Carbon  deposits  will  cause  knocking  in  the 
cylinder.  Near  the  end  of  the  compression  stroke  these  become  in- 
candescent and  premature  ignition  results. 

Crank  chamber  explosions  in  a  two  cycle  engine  are  caused  by  a 
thin  mixture  or  a  retarded  spark.  In  either  case  combustion  is 
not  complete  when  the  admission  port  is  uncovered  and  the  burning 
gases  come  in  contact  with  the  fresh  charge  in  the  admission  pipe 
igniting  them.  The  explosion  transmitted  through  this  pipe  to  the 
crank  chamber  may  be  a  source  of  much  annoyance,  for  frequently 
the  crank  case  cover  gasket  is  blown  out  and  must  be  replaced  to 
keep  the  case  gas  tight. 

A  smoky  exhaust  indicates  too  rich  a  mixture  or  an  excess  of 
lubricating  oil.  In  the  latter  case  the  exhaust  is  black  or  dark 
brown,  burnt  oil  vapor  being  present.  In  the  former  case  the  ex- 
haust is  generally  hazy  and  lighter  and  carries  the  pungent  smell 
of  unburnt  fuel. 

Lost  compression  may  be  due  to  improper  lubrication.  An  im- 
portant point  that  is  often  overlooked  is  that  the  film  of  oil  between 
the  piston  ring  and  cylinder  forms  a  packing,  and,  if  this  is  not 
perfect,  the  gas  will  leak  by  on  the  compression  stroke.  This  is 
technically  known  as  "  blowing."  Other  and  more  frequent  causes 
of  loss  of  compression  are  overheating,  leaky  or  broken  valves  or 
rings,  leaky  spark  plug  gaskets  and  relief  cocks,  and  scored  or  worn 
cylinder  walls. 

Premature  ignition  may  be  produced  by  advancing  the  spark  too 
far,  too  high  compression,  overheating,  overloading  the  engine,  or 


EFFICIENCY,  MANAGEMENT,  OPERATION,  ETC.  89 

by  carbon  deposits  on  the  piston  or  cylinder  heads  becoming  in- 
candescent. The  remedies  are  obvious.  Carbon  deposits  must  be 
removed  periodically.  This  is  generally  done  by  scraping,  although 
there  are  several  reliable  solutions  on  the  market  for  this  purpose. 

Carbureter  defects  are  common  and  numerous.  The  needle  valve 
may  leak  and  flood  the  gasoline  chamber.  This  will  cause  a  very 
rich  mixture,  and  can  be  remedied  by  grinding  the  valve.  The  air 
valve  or  throttle  may  become  stuck.  The  auxiliary  air  valve  spring 
may  not  be  properly  adjusted  to  give  the  correct  mixture  at  high 
speeds.  Water  may  accumulate  in  the  float  chamber,  if  present  in 
the  gasoline.  A  drain  cock  is  generally  provided  to  avoid  this  diffi- 
culty. The  spray  nozzle  may  clog  if  there  is  dirt  in  the  gasoline. 
Gasoline  should  be  thoroughly  strained  through  chamois  before 
putting  it  into  the  tank.  This  will  remove  all  dirt  and  water,  if 
carefully  done.  A  thorough  knowledge  of  the  carbureter  is  essential 
for  successful  operation  of  any  internal  combustion  engine. 

General 

Long  and  Short  Stroke  Motors,  The  proportion  of  cylinder 
diameter  ("  bore  ")  to  stroke  is  a  problem  that  has  caused  more  dis- 
cussion and  resulted  in  less  uniformity  of  opinion  than  any  other 
subject  in  the  internal  combustion  engine  field.  Although  no  dis- 
tinct line  is  drawn  a  motor  that  has  a  stroke  exceeding  1-J  times  the 
bore  is  generally  spoken  of  as  a  "long  stroke"  motor,  and  any 
having  a  smaller  ratio,  as  a  "  short  stroke  "  motor.  As  the  advo- 
cates of  both  types  lay  claim  to  every  conceivable  advantage,  the 
subject  will  not  be  discussed  here  other  than  to  say  that  increasing 
the  stroke  increases  the  expansion  and  also  the  loss  by  radiation 
due  to  the  longer  contact  of  the  gases  each  stroke  with  the  cylinder 
walls.  It  increases  the  piston  speed ;  and  reducing  the  bore  to  main- 
tain the  same  power,  it  increases  the  ratio  of  cylinder  wall  to  cylin- 
der contents,  hence  increases  loss  by  radiation. 

The  duty  for  which  the  motor  is  designed,  the  necessary  piston 


90  IXTKIJXAl,    CoMBrSTIOX    ENG1NK    MANUAL 

speed,  power  required,  weight  allowed  and  initial  compression,  must 
regulate  the  bore  and  stroke  to  a  large  extent. 

Clearance.  The  clearance  volume  is  the  space  enclosed  by  the 
piston  head,  cylinder  walls  and  valve  recesses,  when  the  piston  is  at 
the  beginning  of  its  stroke.  The  proportion  of  the  clearance  volume 
to  the  piston  displacement  is  much  higher  than  in  the  steam  engine, 
because  all  the  medium  is  present  in  the  cylinder  at  the  beginning 
of  the  stroke  instead  of  being  admitted  during  a  fraction  of  the 
stroke  as  in  the  steam  engine.  This  statement  does  not  apply  to  the 
Diesel  and  similar  oil  engines.  Its  value  depends  upon  the  kind 
of  fuel  used,  sometimes  exceeding  35  per  cent.  Obviously  the  higher 
that  the  fuel  can  be  compressed,  the  less  clearance  that  will  be 
necessary. 

Stratification  Theory  and  After  Burning.  This  theory  advanced 
by  Otto  and  so  vigorously  defended  by  Slaby  during  the  Otto  patent 
litigation  assumed  that  in  a  four  cycle  cylinder  the  charge  was  so 
distributed  that  practically  nothing  but  burned  gases  were  next  to 
the  piston  (scavenging  being  imperfect),  next  a  layer  of  poor  mix- 
ture, and  finally  near  the  igniter  the  full  strength  of  the  mixture. 
It  was  further  assumed  that  this  arrangement  was  not  disturbed 
during  compression.  Ignition  was  sure,  but  combustion  was  not 
completed  until  the  piston  had  reached  some  point  along  the  ex- 
pansion stroke.  Thus  Otto  accounted  for  the  slow  drop  in  the  ex- 
pansion line,  and  called  it  "  after  burning/' 

In  view  of  present  information,  it  is  shown  that,  although  strati- 
fication is  not  impossible,  it  does  not  affect  the  economy  or  per- 
formance and  as  a  factor  it  is  not  considered  in  design  or  theory. 
The  phenomenon  of  after  burning  has  also  been  explained  by  the 
"  dissociation  theory/'  At  a  certain  temperature  limit  a  composite 
gas  breaks  up  into  its  elements,  and  at  this  temperature  limit  com- 
bustion cannot  take  place.  If  this  limit  is  reached  at  the  maximum 
compression,  combustion  will  not  occur  until  the  piston  has  reached 
such  a  point  on  the  expansion  stroke  that  the  pressure  and  tem- 
perature has  fallen  below  the  critical  or  dissociation  point.  Con- 
sequently combustion  takes  place  along  the  expansion  line  resulting 
in  the  phenomenon  of  after  burning. 


EFFICIENCY,  MANAGEMENT,  OPERATION,  ETC.  91 

Scavenging.  Scavenging  a  cylinder  consists  of  driving  out  the 
burned  gases  before,  or  simultaneous  with,  the  entrance  of  a  new 
charge.  This  is  very  imperfect  with  an  ordinary  four  cycle  motor, 
for,  at  the  instant  of  admission,  all  the  clearance  volume  is  full  of 
the  burned  gas.  Those  engines  which  receive  the  air  and  fuel 
separately  can  be  scavenged  thoroughly  by  admitting  the  air  while 
the  exhaust  port  is  still  open  and  driving  out  the  exhaust  gases  by 


O  /SO  36o"         see  360  /eo° 

\  __     _  A 

" 


/  Cyc/e    2  5//-oSres.  /Cyc/e 

^•-C^c/e 


V 


0'  ISO  J6O°         /80°  36O*          /SO"         SSO°          S8O°         J6O* 

•4-Cyc/e      -4-  Cy//'rrcfer. 


O"          /So'        360°       /0o°         3&o°        /eo°       360°         /so'        360* 


O'  /&0°  36o°         /Go"  360°         /6o' 

FIG.  58. — Pressure  Diagrams,  Showing  the  Effect  of  Multiplying 

Cylinders. 

this  air  before  the  fuel  valve  opens.  Two  cycle  engines  require 
thorough  scavenging.  A  study  of  the  cycle  shows  that  upon  this 
depends  the  volume  of  fresh  mixture  that  can  be  taken  into  the 
cylinder,  and  as  the  two  cycle  exhausts  just  past  the  center  of  the 
expansion  stroke,  instead  of  at  the  end  as  in  the  four  cycle,  scaveng- 
ing is  of  more  importance  in  the  former  case.  This  is  generally 
accomplished  by  allowing  some  of  the  fresh  charge  to  enter  while  the 
exhaust  port  is  still  open.  A  proper  design  of  exhaust  will  aid 
scavenging  by  giving  the  exhaust  gases  a  high  speed,  causing  a 
tendency  toward  a  partial  vacuum  in  the  exhaust  line. 

Pressure  Diagram.     The  diagrams  in  Fig.  58  show  the  effect  of 


92  INTERNAL  COMBUSTION  ENGINE  MANUAL 

multiplying  the  cylinders  of  an  engine.  They  are  constructed  by 
superposing  the  cards  of  a  one  cylinder  engine  in  the  appropriate 
phase  of  two  successive  cycles.  Similar  diagrams  can  be  made  for 
two  cycle  engines.  The  upper  line,  which  represents  the  pressure 
acting  during  two  complete  cycles,  shows  1080°  or  six  strokes  of  idle 
effort  during  two  cycles.  The  second  line,  which  represents  a  two 
cylinder  engine,  shows  that  pressure  is  acting  50  per  cent  of  the 
time.  It  is  not  until  we  compound  to  six  cylinders  that  we  obtain 
an  overlapping  pressure. 


FIG.  59. — Secondary  Spark  Gap. 

Secondary  Spark  Gap.  (Fig.  59.)  This  is  a  spark  gap  placed  in 
the  secondary  circuit  just  outside  of  the  cylinder.  It  acts  as  a 
condenser,  building  up  the  pressure  on  the  terminal  until  it  can 
leap  the  air  gap,  thus  raising  the  pressure  in  the  circuit  and  strength- 
ening the  spark  at  the  plug.  The  advantages  are : 

a.  Greater  certainty  of  sparking,  because  the  built  up  potential 
will  jump  a  partially  fouled  plug. 

&.  A  means  of  inspecting  the  spark  in  the  cylinder  is  provided, 
for  a  spark  across  the  gap  means  a  spark  at  the  plug. 

Although  not  generally  adopted  at  present,  the  author  believes 
that  such  a  device  could  be  advantageously  employed  in  the  larger^ 
multiple  cylinder  engines.  By  wiring  one  auxiliary  gap  so  that  it 
could  be  cut  into  the  secondary  circuit  of  any  cylinder  at  will,  a 
ready  means  of  testing  the  spark  at  any  plug  is  at  hand,  and  all 


EFFICIENCY,  MANAGEMENT,  OPERATION,  ETC.  93 

work  of  dismounting  the  sparking  apparatus  at  the  engine  for  pur- 
poses of  inspection  is  obviated.  Although  this  would  increase  the 
high  tension  wiring,  no  current  would  be  flowing  in  the  additional 
wire  except  during  the  short  interval  of  testing. 

A  ready  means  of  inspecting  the  spark  in  large  stationary  gas 
plants  is  furnished  by  wiring  an  incandescent  lamp  in  series  with 
each  spark  plug.  Failure  of  this  lamp  to  light  each  cycle  indicates 
absence  of  a  spark  at  the  gap. 


CHAPTER  X 

ENGINES 
The  Koerting-  Two  Cycle  Gas  Engine 

This  engine  illustrates  the  two  cycle  type  with  separate  charging 
pumps.  It  is  double  acting  like  a  steam  engine  and  therefore  the 
end?  of  the  main  motor  cylinders,  the  connecting  rods,  cranks  and 
other  mechanism  for  transmitting  power  from  the  expanding  gas  to 
the  engine  shaft  are  capable  of  design  similar  to  that  used  in  steam 
engine  practice.  The  novel  feature  is  the  mechanism  which  controls 
the  admission  of  the  combustible  gas  to  alternate  sides  of  the  main 
piston.  These  valves  and  pumps  are  explained  in  detail  later. 

The  Koerting-  Cycle 

The  various  steps  of  the  cycle  are  taken  up  in  the  order  in  which 
they  occur. 

1.  The  Exhaust.     In  the  position  shown  in  Fig.  60  the  piston  is 
at  the  end  of  its  out-stroke  and  has  just  uncovered  the  exhaust  ports 
shown  in  the  middle  of  the  cylinder  through  which  the  products  of 
combustion  escape  to  the  atmosphere.    The  escape  of  the  exhaust  is 
hastened  by  the  admission  of  a  quantity  of  air  known  as  the  scaveng- 
ing charge,  which,  being  introduced  under  pressure  behind  the 
burned  gases,  displaces  them  during  the  time  that  the  ports  are 
uncovered  by  the  piston. 

2.  Admission.     At  this  point  the  charging  pumps,  shown  at  the 
side  of  the  cylinder  and  described  more  fully  later,  supply  the 
cylinder  with  a  fresh  charge  of  air  and  gas  which  is  compressed  on 
the  return  stroke  and  ignited  to  do  work  on  the  next  succeeding  out- 
stroke.    The  function  of  the  pumps  is  to  measure,  and  supply  at  the 
proper  instant,  the  right  proportion  of  gas  and  air  necessary  for 
perfect  combustion  in  the  motor  cylinder.    The  charge  is  delivered 
at  a  pressure  of  about  four  pounds. 


96  INTERNAL  COMBUSTION  ENGINE  MANUAL 

3.  Compression.    During  the  return  or  in-stroke  the  admission 
valve  is  closed,  the  exhaust  ports  are  covered  by  the  piston  and  the 
combustible  charge  of  air  and  gas  thus  confined  in  the  cylinder  is 
compressed  by  the  returning  piston  into  the  pre-determined  clear- 
ance space  left  between  the  end  of  the  piston  and  cylinder  head  at 
the  end  of  the  compression  stroke. 

4.  Ignition.     At  the  instant  that  the  engine  passes  the  dead 
center  the  charge  is  ignited  and  the  expansive  energy  of  the  burning 
gases  is  exerted  directly  on  the  piston.    The  engine  being  double 
acting,  the  same  operations  take  place  in  the  opposite  end  of  the 
cylinder,  compression  taking  place  at  one  end,  while  expansion  is 
going  on  at  the  other  end.    From  the  foregoing  it  is  apparent  that 
the  Koerting  cycle  is  on  the  two  cycle  principle. 

The  two  operations  of  expelling  the  products  of  combustion  and 
admitting  the  fresh  charge  are  accomplished  during  the  interval  of 
time  that  the  piston  leaves  the  exhaust  ports  uncovered  as  it  passes 
the  dead  center.  The  pressure  of  the  incoming  gas  being  low  this 
can  be  accomplished  without  the  loss  of  an  appreciable  amount  of 
gas  and  with  only  a  small  loss  of  power,  the  only  requisite  being  that 
the  air  which  forms  the  scavenging  charge  must  be  so  introduced  as 
to  spread  evenly  over  the  whole  area  of  the  cylinder,  forming  a  sepa- 
rating layer  between  the  combustible  mixture  and  the  products  of 
combustion  of  the  preceding  charge.  This  stratification  of  the  gas 
is  accomplished  by  means  of  specially  designed  surfaces  located  in 
each  cylinder  head  just  under  the  admission  valves.  It  prevents  all 
possibility  of  misfire  and  pre-ignition.  These  surfaces  impart  a 
whirling  motion  to  the  air  and  turn  it  back  upon  itself  in  such  a 
way  that  it  forms  an  equally  distributed  layer  over  the  entire  area 
of  the  cylinder. 

Valve  Group  and  Pumps 

There  are  no  exhaust  valves.  The  admission  valves,  one  on  each 
end  of  the  cylinder,  as  shown  in  Figs.  61  and  62,  are  of  the  poppet 
type  positively  actuated  by  means  of  levers  and  push  rods  from  cams 
on  the  main  valve  gear  shaft,  which,  in  turn,  is  driven  by  miter 
gearing  from  the  main  engine  shaft.  The  fresh  charge  of  gas  and 


98 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


air  is  supplied  by  two  charging  pumps  shown  in  Fig.  62.  These 
pumps  are  driven  by  a  crank  and  connecting  rod  from  the  main 
crank  shaft  of  the  engine  and  the  pump  discharge  valves  are  driven 
from  eccentrics  on  the  main  shaft.  Each  end  of  each  pump  dis- 
charges into  a  separate  duct;  and  these  ducts,  which  pass  through, 
the  main  engine  frame,  convey  the  gas  and  air  from  the  crank  end  of 
their  respective  cylinders  to  the  crank  end  of  the  main  cylinder,  and 


FIG.  62. — Valve  Group  of  Koerting  Two  Cycle  Gas  Engine. 

A,  gas  pump.  c,  b,  gas  admission  to  pump. 

B,  air  pump.  /,  gas  discharge  from  pump  to 
p,  pump  discharge  valves.  cylinder. 

from  the  head  ends  of  these  cylinders  to  the  head  end  of  the  main 
cylinder,  as  indicated  diagranimatically  in  Fig.  62. 

As  shown  in  the  figure,  one  gas  and  one  air  channel  terminate 
in  an  annular  opening  concentric  to  and  just  above  each  admission 
valve;  the  inside  duct  leading  to  the  gas  cylinder  and  the  outside 
duct  leading  to  the  air  cylinder.  In  order  to  secure  a  separating 
layer  of  air  between  the  burned  and  fresh  charges  the  gas  pump 
valves  are  so  fixed  that  no  gas  is  delivered  until  after  a  certain  point 


ENGINES  99 

in  its  compression  stroke,  while1  the  air  piston  delivers  throughout 
its  entire  stroke.  The  air,  commencing  to  be  discharged  before  the 
gas,  passes  through  its  discharge  duct,  encounters  the  closed  ad- 
mission valve  and  starts  back  towards  the  gas  cylinder  through  the 
gas  duct,  pushing  the  gas  before  it.  When  the  admission  valve 
opens,  both  ducts  at  first  discharge  air,  and  later  the  one  air  and  the 
other  gas.  The  air  first  discharged  forms  the  scavenging  charge  and 
the  mixture  of  air  and  gas  which  follows,  the  combustible  mixture. 
Since  the  discharge  of  gas  and  air  is  through  separate  ducts  termi- 
nating only  in  the  mixing  chamber  above  the  admission  valve,  no 
explosive  mixture  is  formed  until  this  valve  opens  to  admit  the  fresh 
complement  of  air  and  gas  to  the  main  cylinder. 

General.  The  walls  of  the  main  cylinder,  cylinder  heads  and 
stuffing  boxes  are  cooled  by  water  circulation.  The  cooling  of  the 
piston  is  also  effected  by  water  which  is  introduced  through  the 
hollow  cross-head  pin  and  piston  and  returns  through  a  pipe  inside 
the  hollow  piston  rod.  Ignition  is  by  the  make  and  break  system. 
the  source  of  current  being  by  a  high  tension  oscillating  armature 
magneto,  one  for  each  end  of  the  cylinder.  This  form  of  magneto 
facilitates  starting,  for  one  oscillation  is  sufficient  to  start.  The 
moving  parts  of  the  ignition  plugs  are  operated  by  a  small  shaft 
parallel  to,  and  driven  by,  a  spur  gear  from  the  main  valve  gear 
shaft.  The  point  of  ignition  is  adjustable. 

The  engine  is  started  by  compressed  air.  A  piston  valve  is  pro- 
vided for  admitting  the  compressed  air  to  the  front  and  back  end 
of  the  cylinder  alternately,  just  as  similar  valves  admit  steam  to  a 
steam  engine.  This  piston  valve  is  operated  from  the  cam  shaft 
by  an  eccentric,  and  the  gear  can  be  thrown  into  operation  or  stopped 
instantly  by  means  of  a  special  clutch.  The  manufacturers  claim 
that  the  engine  can  be  started  in  30  seconds.  When  starting  the 
engine  works  like  a  steam  engine,  making  two  or  three  revolutions 
on  compressed  air,  after  which  gas  is  admitted  and  the  compressed 
air  shut  off. 


100 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


ENGINES 


101 


FIG.  64. — The  Sterling  Engine. 


102  INTERNAL  COMBUSTION  ENGINE  .MANUAL 

The  Sterling  Gasoline  Marine  Engine 

An  example  of  excellent  marine  gasoline  engine  is  shown  in  Figs. 
63  and  64.  The  plates  are  self  explanatory.  These  engines  are  built 
in  sizes  ranging  from  8  to  240  horse-power.  The  12  horse-power 
engine  illustrated  is  installed  in  one  of  the  launches  stationed  at  the 
Naval  Academy. 

The  cylinders  are  cast  in  pairs  of  special  hard,  close-grained,  gray 
iron,  the  cylinder  proper  being  chilled  to  present  a  very  hard  sur- 


FIG.  65. — Cylinders  and  Valves. 

face.  The  admission  and  exhaust  valves  are  located  on  opposite 
sides  of  the  cylinder  and  are  all  mechanically  operated  and  are 
interchangeable.  Valve  seats  are  entirely  surrounded  by  water- 
jackets,  and  the  inlet  and  exhaust  passages  are  large  and  free  from 
sharp  bends.  Valve  caps  admit  of  easy  access  to  the  valves  for  in- 
spection. The  large  valve  is  a  good  feature  of  the  design.  The  valve 
stein  guides  are  exceptionally  long,  preventing  leakage  of  the  ex- 
haust, and  also  preventing  the  incoming  charge  from  sucking  air 
past  the  inlet  valve  stem  and  thus  impoverishing  the  mixture. 

The  connecting  rods  are  of  drop  forged  steel  "  I "  section.  The 
upper  end  is  provided  with  a  phosphor  bronze  bushing,  which 
actuates  on  a  hardened  steel  wrist  pin. 


ENGINES 


103 


The  crank  shaft  is  made  of  carbon  steel.  All  bearings  are  ground 
to  size  within  .0005  inch  in  diameter  and  .002  inch  in  length.  The 
forward  end  is  turned  taper  and  has  a  key -way  cut  for  attaching  the 
fly-wheel.  The  crank  shaft  has  three  main  bearings  and  this  is 
known  as  "  three  point  suspension." 


FIG.  66. — Connecting  Rod. 


FIG.  68.— Push  Rod. 


FIG.  67.— Crank  Shaft.     Three  Point  Suspension. 

The  push  rods  which  operate  the  valves  are  of  steel.  The  lower 
end  receives  the  hardened  steel  roller  which  bears  directly  on  the  cam. 
These  rods  are  fitted  with  adjustable  screws  which  admit  of  adjust- 
ment of  the  valves  without  disturbing  any  other  parts.  Push  rod 
guides  are  of  hard  bronze,  supporting  the  push  rod  nearly  its  entire 
length.  This  guide  is  secured  to  the  engine  base  by  stud  bolts. 

The  water  circulating  pump  is  of  the  large  plunger  type  and  ex- 
pansion joints  are  used  on  the  water  connections.  The  exhaust 
manifold  is  water- jacketed  its  full  length. 


104  INTERNAL  COMBUSTION  ENGINE  MANUAL 

The  lubrication  system  is  mechanical.  Oil  is  pumped  from  the 
reservoir  through  the  tubes  to  the  oil  rings  and  the  cam  gears,  and 
from  there  flows  to  the  base,  maintaining  the  necessary  level  of  oil 
for  the  splash  system  that  is  used  for  the  cylinders. 

The  lower  base  is  divided  into  pockets  by  partitions  between  the 
connecting  rods.  This  maintains  a  constant  level  of  oil  regardless 
of  the  pitching  of  the  boat.  Without  these  partitions  all  the  oil 
would  run  to  the  end  of  the  engine  that  is  temporarily  lowest.  The 
crank  pins  are  lubricated  by  oil  which  enters  the  scoop  and  passes 
through  a  duct  in  the  connecting  rod  cap. 

Ignition  is  by  the  jump  spark  system. 

The  Standard  Engine 

This  gasoline  engine  designed  for  marine  use  is  made  in  units  of 
three  cylinders,  and  generally  installed  as  a  two  unit  plant  or  six 
cylinder  engine.  It  is  four  cycle,  double  acting,  having  an  admission 
and  exhaust  valve  for  both  top  and  bottom  of  each  cylinder.  This 
gives  the  engine  the  equivalent  of  twelve  working  cylinders.  The 
engine  is  water  cooled,  as  are  all  the  pistons,  connecting  rods, 
valves,  and  the  exhaust  manifold. 

The  admission  valves  are  all  on  the  front  of  the  engine,  and  are 
mechanically  operated  from  the  same  cam  shaft.  The  exhaust 
valves  on  the  back  of  the  engine  are  similarly  operated  by  another 
cam  shaft.  All  valves  are  mushroom  shaped  of  the  balanced  type. 

To  reduce  the  power  to  one-half  all  the  bottom  admission  valves 
can  be  locked  closed  and  the  exhaust  valves  open,  making  the  engine 
six  cylinder  single  acting.  To  reduce  to  one-fourth  power  the  two 
units  can  be  disconnected  and  one  unit  run  as  a  three  cylinder  single 
acting  engine.  The  engines  are  built  to  250  horse-power  per  three 
cylinder  unit.  A  twin  screw  marine  plant  of  1000  horse-power  can 
be  furnished  by  the  manufacturers. 

The  piston  is  short,  being  somewhat  similar  to  a  steam  engine 
piston,  and  a  cross  head  and  guide  are  present  in  consequence.  The 
piston  rod  works  through  a  metallic  packed  stuffing  box  to  make 
the  bottom  end  of  the  cylinder  gas  tight.  The  oiling  and  cooling 
systems  for  such  a  large  engine  are  necessarily  elaborate,  but  these 


FIG.  69. — Standard  Engine. 


10(J  I  vn.KNAi,  COM  iirsTiox    KN<;IM-:   MAMAL 

difficulties  arc  cleverly  overcome,  and,  due  to  good  design,  the  engine 
is  ipiiel  and  five  From  vibration.  Lubrication  is  by  the  forced  feed 
system. 

In  Fig.  (ill,  .1  is  the  gas  inlet,  />'  the  top  admis-ion.  ('  the  top 
exhaust,  and  /)  the  exhaust  outlet.  It  is  apparent  that  this  will 
operate  as  a  four  c}rcle  engine.  On  the  bottom  end,  7>,  is  the  bottom 
admission,  and  C^  the  bottom  exhaust.  This  end  also  acts  as  an  in- 
dependent four  cycle  engine.  E  and  F  are  the  cam  shafts  that 
operate  the  admission  and  exhaust  valves  respectively. 

Ignition  is  by  the 'make  and  break  >ystem. 

The  admission  pipe  runs  along  the  center  line  ol'  the  cylinders 
in  front  of  them  and  sends  a  branch  to  each  end  of  each  cylinder. 
The  engine  is  operated  by  the  two  levers  G  and  //  shown  on  the 
front,  of  the  engine.  G  is  the  spark  lever.  The  lever  II  operates  a 
eompresscd  air  valve  which,  in  turn,  can  shift  the  admission  valve 
en.ni  shaft  in  the  direction  of  its  length.  This  shaft  carries  three 
sets  of  cams.  One  operates  the  admission  valves  for  the  ahead  direc- 
tion, one  for  the  reverse  direction,  and  one  set  operates  ail1  valves 
in  the  bottom  of  the  three  after  cylinders  for  starting  and  reversing. 

To  start,  shift  the  cam  shaft  so  that  the  three  after  cylinders 
work  on  compressed  air.  The  three  forward  ones  are  on  gasoline. 
After  a  few  revolutions  on  air  the  forward  cylinders  will  start,  to 
run  by  fuel.  Shift  the  lever  until  all  the  cylinders  are  on  gasoline. 

To  reverse  from  the  go-ahead  direction,  shift  the  shaft  part  way 
over  so  that  the  air  valves  are  in  operation.  Shut  off  the  fuel  and 
open  the  air  throttle.  As  soon  as  the  er.gine  is  started  in  the  reverse 
direction  by  the  air.  start  on  fuel  and  throw  the  lever  all  the  way 
over  to  the  reverse  direction.  When  the  air  valve  cams  are  operating 
the  air  valves  on  the  bottom  of  the  three  after  cylinders,  other  cams 
are  holding  tin1  top  exhaust  valves  of  these  cylinders  open. 

The  Gnome  Engine 

Tlu«  (Jnome  engine  is  built  in  two  sixes.  ~>0  horse-power  and  100 
horse-power.  A  1  l<>  horse-power  engine  is  being  constructed  for 
the  Gordon  Kennett  cup  race.  It  is  used  for  aeroplanes  exclusively. 
The  ."»()  horse-power  (  Fig.  |0)  has  7  cylinders  and  the  100  horse- 


ENGINES 


10' 


power  has  14,  7  being  in  one  plane  and  7  in  a  parallel  plane,  those 
of  the  second  group  being  staggered  with  those  of  the  first.  It  is  a 
gasoline  radial,  rotary,  air  cooled  engine.  The  crank  shaft  is  sta- 
tionary and  the  cylinders  revolve  about  it.  This  gives  the  same 
relative  motion  of  the  pistons  to  the  cylinders  as  if  the  cylinders 
were  stationary  and  the  crank  revolved.  The  crank  shaft  is  secured 
to  the  aeroplane.  The  propeller  is  made  fast  to  the  front  of  the 
cylinders  and  revolves  with  them. 


FIG.  70.— Gnome  50-H.  P.  Engine. 


The  carbureter  is  in  the  rear  of  the  engine  and  the  charge  passes 
through  the  hollow  crank  shaft  to  the  crank  case.  Automatic  inlet 
valves  in  the  piston  heads  admit  the  charge  to  the  cylinder.  The 
exhaust  valves  which  are  in  the  cylinder  heads  are  mechanically 
operated  from  the  shaft  and  the  ignition  circuits  to  the  plugs  are 
also  completed  by  contacts  on  the  shaft.  Ignition  is  by  a  high  ten- 
sion magneto  and  the  point  of  ignition  is  not  adjustable  by  hand. 
At  low  speed  the  spark  is  retarded  and  as  the  engine  speed  is  in- 
creased the  spark  is  advanced  automatically  by  the  consequent  in- 
crease of  speed  of  the  magneto.  Lubrication  is  by  forced  feed.  The 
cylinders  are  made  of  solid  steel  and  are  secured  to  the  crank  case  by 
an  ingenious  ring.  Experiments  are  being  conducted  with  an  engine 
of  this  type  having  mechanical  inlet  valves. 


108  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Knight  Slide  Valve  Motor 

The  poppet  type  of  valve  has  been  used  in  all  practical  four- 
cycle internal  combustion  engines  until  recent  years,  but  the  adop- 
tion after  exhaustive  tests  of  this  motor  in  the  Stearns  and 
Columbia  automobiles  in  this  country,  and  the  Diamler  and  nu- 
merous others  abroad,  has  again  drawn  attention  to  slide  valve 
construction.  The  difficulty  of  keeping  the  ordinary  slide  valve 
gas  tight  and  of  providing  sufficient  lubrication  at  the  high  work- 
ing temperature  of  the  gases  has  made  its  use  impractical. 

The  impact  of  poppet  valves  on  their  seats,  and  the  cams,  springs, 
etc.,  which  operate  them,  are  the  source  of  noise  in  an  engine. 
This  noise  is  eliminated  in  the  Knight  motor.  The  principal  ad- 
vantage claimed  for  this  valve  mechanism  is  that  the  inlet  and  ex- 
haust passages  are  fully  twice  the  size  of  the  gas  passage  obtain- 
able in  a  liberal  design  of  the  tee-head  poppet  valve  motor,  and 
nearly  three  times  the  size  of  the  gas  passages  in  the  ell-head  or 
valve-in-head  motor. 

Figs.  70a,  70b  and  70c  show  the  general  features  of  design  as 
adopted  by  the  United  Motor  Company  in  the  Columbia.  The 
cylinder  heads  are  removable.  They  are  depressed,  water-cooled 
and  contain  two  spark  plugs  for  Bosch  or  other  double  ignition. 
The  valves  for  each  cylinder  consist  of  two  sleeves  made  of  Swedish 
grey  iron.  Being  very  thin  there  is  no  limit  to  the  degree  of  hard- 
ness attainable.  Both  inner  and  outer  sleeves  are  open  at  both 
ends  and  t  each  sleeve  has  openings  on  two  sides.  These  sleeves 
are  reciprocated  to  perform  the  valve  function  by  short  connecting 
rods  actuated  by  a  lay  crankshaft  at  half  speed  by  "  Coventry " 
silent  chain.  , 

As  seen  from  the  cuts  the  outer  sleeve,  driven  by  a  connecting  rod 
from  a  countershaft  on  the  right,  Fig.  70b,  moves  up  and  down  be- 
tween the  cylinder  wall  and  the  inner  sleeve.  The  inner  sleeve, 
driven  by  its  connecting  rod  from  the  same  countershaft,  Fig.  70a, 
moves  up  and  down  between  the  outer  -sleeve  and  the  piston.  The 
inner  wall  of  this  inner  sleeve  forms  the  combustion  chamber  wall. 

The  travel  of  the  sleeves  is  only  about  one  inch  and  the  power  re- 
quired to  overcome  their  friction  and  drive  them  is  no  greater  than 
that  necessary  to  actuate  poppet  valves  for  an  engine  of  the  same  size. 


FIG.  70a. — Columbia  Knight  Motor,  Showing  Sleeve-Valve  Arrangement. 


FIG.  7  Ob. — Columbia  Knight  Motor,  Cross-Section  View. 


110 


INTERNAL  COMBUSTION  ENUINK  "MANUAL 


Operation.  During  ihe  suction  stroke  the  right-hand  slots  of 
the  inner  and  outer  .sleeves  register,  forming  a  large  opening  for 
the  charge  to  enter.  At  the  end  of  the  suction  stroke  one  sleeve 
moves  up  and  the  other  down,  closing  the  opening,,  and  the  com- 
pression stroke  takes  place.  Compression  heing  accomplished  the 
charge  is  fired  in  the  usual  way  and  the  combustion  or  power  stroke 
takes  place,  all  slots  still  being  out  of  register.  At  the  end  of  the 
power  stroke,  movement  of  the  sleeves  brings  the  left-hand  slots 
into  register,  and  the  opening  thus  formed  is  a  large  exhaust  for 
the  gases.  This  is  best  illustrated  by.  Fig.  70d,  which  is  published 
by  courtesy  of  the  >Y/V ///>//>  .1  nirri-can. 

The  eccentric  operating  the  inner  sleeve  is  given  a  certain  advance 
or  "  lead  "  over  that  of  the  outer  sleeve.  This  lead,  together  with 
the  rotation  of  the  eccentric  shaft  at  half  the  crank  shaft  speed, 
produces  the  cycle  of  operations. 


Fi(i.  70c.— Details  of  the  Columbia  Knight  Motor. 


In  the  first  diagram.  Fig.  I0d,  the  piston  is  just  past  its  top  center,, 
and  is  starting  down  on  the  inlet  stroke.  The  inner  sleeve  is  at  the 
bottom  of  its  travel  and  moving  slowly  upward,  the  outer  sleeve  is 
about  midway  in  its  travel  and  is  moving  downward  rapidly.  The 
opening  from  the  carbureter  through  the  inlet  port  into  the  cylinder 
is  a  rapidly  increasing  space  between  the  upper  edge  of  the  slot  in  the 
inner  sleeve  and  the  lower  edge  of  the  slot  in  the  outer  sleeve.  By 
i In-  lime  the  piston  is  a  little  more  than  half  way  down  on  the  suc- 
tion  stroke  the  inlet  passage  is  wide  open  as  shown  in  the  second 
diagram  of  Fig.  70d.  The  outer  sleeve  is  now  at  the  bottom  of  its 
stroke  and  moving  very  slowly,  the  inner  sleeve  is  gaining  in  speed 
moving  upward,  and  the  inlet  is  closed  by  the  lower  edge  of  the 
inner  sleeve  slot  passing  the  upper  edge  of  the  outer  sleeve  slot,  as 


ENGINES 


111 


shown  in  the  third  diagram  of  Fig.  70d.  The  inner  sleeve  con- 
tinues to  move  up  with  the  piston  on  its  compression  stroke,  the 
rings  in  the  head  and  piston  tightly  sealing  the  compression  space, 
until  the  explosion  occurs.  The  sleeves  and  piston  are  then  in  the 
position  shown  in  the  fourth  diagram.  About  two-thirds  of  the  way 
down  on  the  explosion  stroke  of  the  motor  the  exhaust  passage 
begins  to  open.  The  inner  sleeve  is  moving  down  with  the  piston, 
and  the  passage  is  between  the  lower  edge  of  the  inner  sleeve  slot 
and  the  lower  edge  of  the  junk-ring  in  the  head,  the  outer  sleeve 
being  practically  stationary  at  the  top  of  its  stroke.  The  outer 
sleeve  starts  on  its  downward  stroke,  and,  gaining  in  speed  as  the 
inner  loses,  leaves  a  clear  opening  for  the  exhaust.  The  piston  is 
now  one-third  up  on  its  exhaust  stroke,  and  the  passage  is  closed  by 
lite  upper  edge  of  the  outer  sleeve  slot  in  passing  the  lower  edge  of 
the  exhaust  port  in  the  cylinder,  as  the  piston  reaches  its  top  center. 


:>p*-ns.      2.  Inlet  o 


Inlet  closes.        4.  Top  of         5.  Exhaust  open*.       6.  Exhaust  open.    7.  Exhaust  closes, 
compression  stroke. 


FIG.  70d. — Relative  Positions  of  Sleeves  and  Piston  in  the 
Operation  of  the  Knight  Engine. 

The  four  cycles  or  strokes  of  the  engine  (suction,  compression,  ex- 
plosion, and  exhaust)  have  now  been  completed;  the  crank  has 
turned  twice;  the  eccentrics  have  driven  the  sleeves  once,  and  the 
cycle  of  operation  is  now  ready  to  be  repeated. 

The  timing  shown  is  not  different  from  that  ordinarily  used  in 
poppet  valve  engines.  Any  timing  of  the  valves  can  be  secured, 
however,  by  varying  the  "  lead  "  between  the  eccentrics  that  operate 
the  two  sleeves  and  by  properly  locating  the  slots  in  the  sleeves. 
The  amount  of  valve  opening  is  practically  unlimited  and  is  gov- 
erned by  the  width  of  the  slot  in  the  sleeves  and  the  "throw"  of 
the  eccentrics  that  drive  and  determine  the  travel  of  the  sleeves. 

Lubrication.  Oiling  by  the  Columbia  movable  dam  system  in- 
sures the  exact  amount  of  lubricant  that  the  motor  speed  demands. 
Oil  is  forced  into  the  main  bearings  by  a  pump.  The  same  pump 


112 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


forces  oil  into  troughs  set  transversely  beneath  the  connecting  rods, 
and  the  rod  scoops  dipping  into  these  troughs  splash  oil  to  the 
cylinders  and  sleeves.  These  troughs  are  connected  to  a  buss  shaft 


FIG.  71. 

which,  being  operated  by  the  throttle,  raises  or  lowers  the  troughs 
as  the  throttle  is  opened  or  closed.  The  troughs  therefore  hold 
more  or  less  lubricant  and  the  scoops  dip  in  deeply  or  lightly  as 
the  motor  runs  fast  or  slow. 

Lubrication  experiments  are  under  way,  and  probably  in  the 
near  future  the  design  will  embody  means  of  supplying  oil  to  the 
tops  of  the  sleeves  by  forced  feed.  Circumferential  grooves  on  the 


ENGINES 


113 


outer  surface  of  the  sleeve  divides  this  surface  into  a  series  of  oil 
rings,  thus  aiding  lubrication. 

As  this  may  possibly  be  the  ultimate  type  of  gasoline  engine, 
experiments  along  this  line  should  be  watched  with  interest. 

The  Mietz  and  Weiss  Marine  Oil  Engine 

The  Mietz  and  Weiss  marine  oil  engine  operates  on  kerosene,  fuel 
or  crude  oil;  the  fuel  is  injected  directly  into  the  cylinder.  The 
manufacturers  claim  a  consumption  of  one  pint  of  oil  per  horse- 
power hour  under  full  load  and  a  decrease  in  consumption  in  almost 
direct  proportion  to  the  decrease  in  load  plus  the  idle  consumption 
(amount  required  to  overcome  friction).  It  is  a  form  of  two  cycle 
engine  receiving  one  impulse  every  revolution. 

Fig.  71  shows  a  cross  section  of  the  engine.  The  piston  is  of  the 
trunk  pattern  fitted  with  cast  iron  packing  rings.  The  cylinders 

are  amply  water- jacketed ; 
the  circulation  is  by  a  rotary 
pump  driven  by  gear  from 
the  main  shaft.  Circulat- 
ing water  enters  the  base  of 
the  jacket,  is  forced  up  to 
the  top  and  is  led  into  the 
exhaust  pipe  to  prevent 
overheating  of  the  latter. 
This  is  a  common  marine 
practice. 

Fuel  is  supplied  by  a 
pump  which  is  regulated  by 
a  governor  so  that  the 
amount  of  fuel  supplied  is  a 
function  of  the  speed  and 
load.  The  fuel  enters  the 
PIG.  72.  cylinder  by  the  pipe  57 

and     encounters     the     hot 

bulb  64,  which  vaporizes  and  ignites  it.  Waste  gases  pass  out  at  the 
exhaust  139.  When  the  engine  is  to  be  started  cold  the  bulb  must 
be  heated  to  dull  red  heat  by  an  external  burner  176.  The  details 
of  this  arrangement  are  shown  in  Fig.  72.  After  the  first  explosion 
the  bulb  will  retain  its  heat  and  the  ignition  is  by  a  combination  of 
compression  and  hot  bulb. 


Sectional  View  of  Starting  Lamp  Showing  Burner 
and  Blowpipe. 


114  INTERNAL  COM  msTinx    KNUINK   MAM  AL 

Lubrication  is  by  the  forced  feed  type,  the  oil  pump  consisting  of 
a  plunger  worked  by  a  ratchet,  the  lubrication  of  the  cylinder, 
piston,  crank  pins,  shaft  bearings  and  connecting  rods  being  abso- 
lutely automatic.  An  engine  of  this  general  type  is  installed  in  the 
laboratory. 

The  American  Diesel  Engine 

This  engine,  the  invention  of  Mr.  Eudolph  Diesel,  of  Munich,  re- 
ceived most  of  its  early  development  in  this  country.  It  is  a  vertical, 
four  cycle,  single  acting  engine,  Fig.  73.  The  manufacturers  claim 
that  it  has  "  double  the  efficiency  of  the  most  perfect  triple  expan- 
sion engine,  and  fifty  per  cent  greater  than  the  hitherto  best  gas  or 
oil  engine."  This  type  could  be  made  very  suitable  for  marine  use. 

It  differs  from  all  previous  internal  combustion  engines  in  com- 
pressing a  full  charge  of  air  to  a  point  above  the  ignition  point  of 
the  fuel,  then  injecting  the  fuel  for  a  certain  period  (variable  ac- 
cording to  the  load)  into  this  incandescent  air  where  it  burns  with 
limits  of  temperature  and  pressure  under  perfect  control.  Instead 
of  a  sudden  explosion,  the  action  is  a  steady  combustion  at  a  pre- 
determined temperature,  the  combustion  line  being  practically  an 
isothermal. 

Fuel  is  pumped  to  the  fuel  chamber  by  a  fuel  pump.  A  two 
stage  compressor,  generally  driven  from  the  main  shaft,  serves 
to  compress  air  to  about  800  pounds  pressure.  This  air  is  cooled 
before  use,  and  is  used  only  to  inject  the  fuel  from  the  fuel 
chamber  to  the  cylinder,  and  to  charge  an  air  tank  for  starting 
the  engine  when  cold.  An  extremely  sensitive  governor  controls  the 
quantity  of  fuel  injected  each  stroke.  So  fine  is  this  regulation  that 
the  engine  is  used  to  operate  alternating  current  generators  in 
parallel  without  difficulty. 

The  fuel  used  at  half  load  rarely  exceeds  55  per  cent  of  that  used 
at  full  load,  so  the  consumption  is  nearly  proportional  to  the  work 
done.  This  very  marked  contrast  to  the  performance  of  other  types 
of  engines  is  the  result  of  features  inherent  in  the  Diesel  cycle  alone, 
and  is  due  to  direct  regulation  of  the  fuel  supply  by  the  governor. 
The  engine  is  guaranteed  a  consumption  not  to  exceed  8  gallons  of 


ENGINES 


115 


FIG.  73.— Diesel  Engine. 


116  INTERNAL  COMBUSTION  ENGINE  MANUAL 

suitable  crude  or  fuel  oil  for  each  100  net  effective  horse-power  hours 
(brake  horse-power  hours)  when  running  at  any  load  between  half 
load  and  rated  capacity.  This  gives  power  at  less  than  one-fourth 
cent  per  brake  horse-power.  An  efficiency  of  38  per  cent  has  been 
attained.  Any  good  crude  or  fuel  oil  can  be  used  as  fuel. 

CYCLE  OF  OPERATIONS 

As  stated  above,  the  fuel  is  not  compressed,  only  air  being  in  the 
cylinder  during  this  stage  of  the  cycle,  hence  pre-ignition  is  im- 
possible. The  clearance  is  small,  being  only  -J  inch  for  a  120  horse- 
power engine.  The  complete  cycle  is  as  follows: 

1.  Aspiration  Stroke.     The  piston  moves  to  the  bottom  of  the 
cylinder  and  during  this  stroke  the  air  admission  valve  opens  and 
allows  the  cylinder  to  fill  with  air  at  atmospheric  pressure. 

2.  Compression  Stroke.     The  piston  moves  to  the  upper  end  of 
the  cylinder.    During  this  stroke  the  admission  valve  is  closed  and 
the  air  in  the  cylinder  is  compressed  to  500  pounds  per  square  inch, 
at  which  pressure  its  temperature  is  sufficient  to  ignite  any  form  of 
petroleum  (crude  or  refined)   spontaneously.     No  valves  are  open 
during  this  stroke  and  there  is  nothing  in  the  cylinder  but  pure  air. 

3.  Expansion  Stroke.     When  the  piston  has  reached  the  top  of 
the  compression  stroke  and  the  crank  is  just  crossing  the  dead  center, 
a  small  needle  valve,  Fig.  74,  opens  and  a  charge  of  liquid  fuel  mixed 
with  compressed  air  is  blown  into  the  incandescent  air  already  in  the 
cylinder.     Ignition  takes  place  as  the  fuel  comes  in  contact  with 
this  hot  air.     The  fuel  valve,  together  with  the  air  and  exhaust 
valves,  is  placed  at  the  side  of  the  cylinder  at  the  top  end,  and  all 
valves  open  into  the  same  space.    The  quantity  of  fuel  is  not  all 
blown  in  at  once;  instead,  fuel  injection  is  maintained  for  a  period 
equal  to  10  per  cent  of  the  downward  stroke  of  the  piston.     It 
would  be  impossible  to  maintain  this  long  period  of  admission  if 
fuel  alone  were  injected,  but  the  compressed  air,  which  is  blown  in 
with  the  fuel  and  which  is  thoroughly  mixed  with  the  fuel  by  the 
perforated  washers  that  surround  the  needle  valve,  increases  the 


ENGINES  117 

volume  and  thus  gives  a  quantity  whose  injection  can  be  controlled. 
The  compressed  air  referred  to  is  that  supplied  by  the  two  stage 
compressor  at  800  pounds  pressure  and  cooled  before  introduction  to 
the  fuel  valve. 

After  the  needle  valve  closes,  the  hot  gases  expand  until  the  piston 
has  traveled  90  per  cent  of  its  stroke,  when  the  exhaust  opens  to 
relieve  the  pressure.  The  pressure  at  opening  of  the  exhaust  valve 
for  normal  load  is  generally  35  pounds  per  square  inch,  and  the 
temperature  about  700°  F.  The  pressure  in  the  cylinder  is  not  due 
to  the  expansion  of  gases  of  combustion  alone,  for  there  is  a  large 
excess  of  air  present  and  the  high  heat  attained  is  sufficient  to  ex- 
pand this  excess  air  also. 

4.  Exhaust  Stroke.  This  fourth  and  last  stroke  of  the  cycle  takes 
place  on  the  upward  stroke.  The  exhaust  valve  is  open  and  the  hot 
gases  are  forced  out  by  the  piston.  When  the  piston  reaches  the  top 
center,  the  exhaust  valve  closes,  the  admission  valve  begins  to  open 
and  the  cycle  is  repeated. 

The  engine  is  water  cooled  and  the  valves  are  operated  as  shown 
in  Fig.  73.  A  is  a  cam  on  the  countershaft,  B  is  the  cross  rod  witli 
a  roller  bearing  on  the  cam  A,  and  C  is  the  push  rod  that  actuates 
the  valve  stem.  Splash  lubrication  is  used  for  the  cylinder,  and  the 
main  bearings  are  lubricated  by  an  oil  ring  and  an  oil  chamber. 
The  fuel  valve  is  made  of  nickel  steel  to  prevent  abrasion  by  the 
petroleum.  The  piston  is  of  the  long  trunk  type,  being  approxi- 
mately 2?}  times  the  diameter  in  length,  tapering  1/32  inch,  and 
provided  with  four  snap  rings. 

Governor.  The  governor  is  connected  to  a  by-pass  at  the  fuel 
pump.  The  pump  runs  at  constant  speed.  If  the  load  is  light  and 
the  fuel  requirement  is  low,  the  governor  holds  the  by-pass  valve 
open  and  allows  a  large  amount  of  oil  to  return  to  the  suction  side 
of  the  pump ;  when  the  load  increases,  more  oil  is  required ;  the  gov- 
ernor holds  the  by-pass  open  for  a  shorter  period,  less  oil  goes  back 
to  the  pump  suction  and  more  goes  to  the  engine. 


118 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


Valve  Group.  The  group  consists  of  the  air  and  exhaust  valves, 
which  require  no  special  consideration,  and  the  fuel  valve.  This  last 
consists  of  a  needle  valve  A  which  is  cam  actuated  through  the  bell 
crank  lever  D,  always  opening  for  the  same  length  of  time  each 


FIG.  74. — Valve  Group,  Diesel  Engine. 

cycle.  Fuel  is  introduced  through  the  pipe  B,  the  amount  being 
regulated  by  the  governor  for  each  cycle  as  stated  above.  Com- 
pressed air,  which  is  previously  cooled,  enters  at  C  and  the  per- 
forated washers  E  serve  to  mix  this  air  with  the  fuel.  When  the 
needle  valve  is  opened  the  compressed  air  blows  the  fuel  into  the 
cylinder. 


I 


I       i 


in  M   Aii  I 

U&MM 


ENGINES 


Details  of  20th  Century  Engine 

The  20th  Century  gasoline  marine  engine  is  of  the  4  cycle  type. 
A  12  horse-power  engine  is  installed  in  one  of  the  launches  at  the 
Naval  Academy.  It  is  illustrated  in  Figs.  75  and  76,  which  are 


self  explanatory, 
details. 


Figs.   77-79   show   some  of  the   constructional 


FIG.  77.— Carbureter. 


PIG.  79. — Piston,  Rings,  Rod 
and  Bearings. 


FIG.  78.— Igniter 


122  INTERNAL  COMBUSTION  ENGINE  MANUAL 

The  Jaeger  Engine 

A  view  of  the  Jaeger  gasoline  marine  engine,  which  is  installed 
in  one  of  the  launches  at  the  Naval  Academy,  is  shown  in  Fig.  80 
which  requires  no  explanation. 

The  Alcohol  Engine 

The  problem  of  alcohol  vaporization  was  discussed  under  the 
chapter  on  carburetion.  The  compression  is  carried  higher  than  in 
other  liquid  fuel  engines.  Eecent  experiments  show  that  the  alcohol 
engine  can  be  started  cold.  The  Deutz  Company  spray  the  alcohol 
into  the  admission  line  near  the  inlet  valve.  In  appearance  the 
engine  is  like  an  ordinary  four  cycle  gasoline  engine,  but  in 
design,  since  the  useful  effect  of  a  given  weight  of  denaturized 
alcohol  is  0.7  that  of  an  equal  weight  of  gasoline,  the  cylinder 
dimensions,  inlet  and  exhaust  passages,  are  increased  in  the  ratio 
of  1.4  to  1  to  get  equal  power.  This  increase  and  the  modified  car- 
bureter are  the  only  points  wherein  the  alcohol  engine  differs  from 
the  gasoline  engine.  A  mixture  of  equal  weights  of  gasoline  and 
alcohol  gives  a  very  efficient  performance  in  the  gasoline  engine 
without  necessitating  change  of  cylinder  design. 

Naphtha  and  Alco-Vapor  Engines 

These  engines,  which  are  really  external  combustion  engines,  differ 
from  each  other  only  in  the  medium  used.  Naphtha  engines  use 
naphtha  vapor  and  alco-vapor  engines  use  alcohol  vapor  for  their 
mediums.  In  both  cases  the  medium  is  heated  in  an  external  retort 
and  the  vapor  tension  thus  produced  is  used  to  drive  the  piston  in 
a  similar  manner  to  the  steam  engine.  The  advantage  lies  in  the 
increased  vapor  tension  of  either  of  these  mediums  over  steam.  In 
construction  the  engine  differs  from  the  internal  combustion  engine 
in  having  small  clearance  and  slide  valves.  It  works  on  the  steam 
engine  cycle.  It  is  built  in  sizes  from  1  to  10  horse-power  and  is 
suitable  for  use  in  -small  launches. 


ENGINES 


123 


124: 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


Reversing 

Small  engines,  if  reversible,  can  be  reversed  by  hand,  but  large 
reversible  engines  require  an  auxiliary,  such  as  compressed  air  to 
reverse  them.  However,  but  few  engines  are  reversible,  so  it  becomes 
necessary  in  marine  practice  to  employ  some  method  of  reversing  the 
direction  of  propeller  rotation  relative  to  the  engine  shaft.  The 
gear  installed  in  the  laboratory  is  shown  in  Fig.  81.  0  is  the  engine 


FIG.  81. 

crank  shaft  carrying  the  bevel  wheel  C.  H  is  the  propeller  shaft 
which  carries  the  bevel  wheel  D.  F  is  a  pinion  which  is  carried  in 
bearings  cast  to  the  casing  B,  and  meshing  with  the  bevel  wheels  C 
and  D.  A  and  E  are  two  friction  collars  operated  by  the  reversing 
lever  through  a  clutch  in  such  a  manner  that  either  can  be  locked 
to  the  casing  B,  the  other  being  simultaneously  unlocked.  A  is 
made  fast  to  the  bed  plate  or  other  stationary  part  of  the  engine  or 
boat.  E  is  firmly  fixed  to  the  propeller  shaft  H.  The  operation  is  as 
follows:  When  going  ahead  the  casing  B  is  free  to  rotate,  the 
friction  band  A  being  unlocked.  At  the  same  time  the  friction  band 


ENGINES  125 

E  is  locked  to  the  casing  so  that  it  will  revolve  with  the  casing.  This 
locks  all  the  spur  wheels,  and  the  casing  will  now  revolve  with  the 
engine  crank  shaft  driving  the  propeller  shaft  as  it  is  also  locked  to 
the  casing.  To  reverse,  throw  the  clutch  to  the  right,  releasing  the 
friction  band  E.  At  the  same  time  the  friction  band  A  is  locked 
making  the  casing  stationary.  Rotation  of  the  engine  shaft  is 
communicated  through  the  pinion  F,  which  now  has  a  stationary 
bearing,  to  the  spur  wheel  on  the  propeller  shaft  H.  The  gears  re- 
duce the  speed  on  reverse  direction.  There  are  three  pinions  like  F 
spaced  at  equal  intervals  around  the  casing. 


CHAPTER  XI 
GAS  PRODUCERS 

The  gas  producer  furnishes  an  economical  means  of  generating  a 
suitable  gas  for  use  in  ail  internal  combustion  engine.  This  field 
has  received  considerable  attention  both  in  this  country  and  abroad. 
It  is  especially  applicable  to  stationary  plants,  but  has  been  suc- 
cessfully tried  in  marine  practice.  At  present  there  is  a  steamer 
on  Chesapeake  Bay  operated  by  a  producer  plant. 

Reactions.  Steam  and  air  are  blown  or  drawn  through  a  thick 
bed  of  coal.  The  result  is  decomposition  of  the  water  vapor  to  H2  and 
0,  and  the  combination  of  this  liberated  0  and  the  0  in  the  air  with 
the  carbon  in- the  fuel  to  form  C02  and  CO.  Fig.  82  gives  an  idea 
of  the  reactions  in  the  generator.  As  the  object  is  to  produce  a 
combustible  gas,  the  aim  is  to  completely  burn  as  little  carbon  as 
possible  and  to  convert  as  much  as  possible  to  CO.  It  is  necessary 
to  burn  a  certain  amount  to  CO 2  in  the  first  zone  to  furnish  to  the 
second  zone  enough  heat  to  convert  the  C02  into  CO. 

Fuels  Used.  Anthracite  coal  is  the  most  efficient  fuel  that  can 
be  used  in  a  producer  plant.  This  is  generally  in  the  form  of 
anthracite  peas  on  account  of  its  cheapness.  Non-caking  bituminous 
coal,  gas  coke,  and  occasionally  charcoal,  are  also  used.  The  fol- 
lowing table  shows  the  approximate  composition  of  the  various  fuels 
used  in  producers : 

Volatile 
Fuel.  Carbon.          Matter.  Ash. 

Anthracite   92%  6%  1.5% 

Non-caking  bituminous 70%  20%  8    % 

Gas  coke   85%  6%  9    % 

The  last  two  factors,  percentage  of  volatile  matter  and  ash,  have 
the  most  influence  on  the  success  or  non-success  of  the  producer. 
The  volatile  products,  which  are  present  in  large  quantities  in 
bituminous  coal,  distill  off  in  the  form  of  tarry  vapors,  and  these 


GAS  PRODUCERS 


127 


are  extremely  difficult  to  clean  out  of  the  gas.  This  necessitates  an 
•elaborate  and  expensive  scrubber  for  bituminous  fuel.  The  per- 
centage of  volatile  matter  in  gas  coke  does  not  exceed  that  in  an- 


>::_'m.';the;  Coal.  ;•"."/: \''. 

•;Temperature  about     "  .  .* 
'     1300-be'grees  Fahr."' .   -\  ' 

"  ' •  •  •      -    * * 


I  Decomposition'   Zo.ne  . 
•CO2 


Temperature  about  1900  Fa'hr:  . 


Combustion'  Zone.  ' 
C  +  2O=C.O2   .  - 


FIG.  82. — Schematic  Plan  of  Producer  Showing  Zones  in 
Fuel  Bed  and  Reactions  that  Take  Place. 

thracite  coal,  but  is  of  a  more  tarry  nature.  The  amount  of  ash 
present  is  of  importance,  for  the  fusion  of  this  ash  forms  hard 
clinkers  which  may  block  up  the  fire  and  prevent  the  necessary 
reactions  for  producing  good  gas. 


128  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Classification.  Gas-producer  plants  may  be  divided  into  three 
classes  according  to  the  method  of  furnishing  air  and  steam  to  the 
fuel: 

1.  Suction  Producers.    In  this  type  the  air  and  steam  are  drawn 
through  the  fuel  by  the  suction  of  the  engine  on  the  aspiration 
stroke. 

2.  Pressure  Producers.    In  these  air  and  steam  are  forced  through 
the  fuel  by  a  fan  or  blower. 

3.  Combination  Producers.     This  system  has  a  fan  between  the 
generator   and   the  engine.     This   fan   draws  the  air  and   steam 
through  the  producer  and  forces  the  gas  generated  to  the  engine. 
The  generator  is  therefore  of  the  suction  type  and  the  remainder  of 
the  plant  is  of  the  pressure  type. 

The  Suction  Producer 

A  suction-producer  plant  consists  of  four  essential  parts : 

1.  The  generator. 

2.  The  vaporizer. 

3.  The  scrubber. 

4.  The  purifier,  which  also  "acts  as  an  expansion  box. 

The  operation  of  a  suction  producer  is  best  illustrated  by  the 
earliest  practical  producer,  which  was  shown  by  H.  Cerdes  to  the 
Society  of  German  Mechanical  Engineers,  Fig.  83.  This  is  used 
as  an  example  because  of  its  simplicity.  Modern  improvements  are 
shown  later. 

Fuel  is  supplied  through  the  hopper.  The  engine  when  running 
creates  a  partial  vacuum  throughout  the  plant.  Air  for  combustion 
enters  at  the  air  inlet,  and  in  modern  practice  is  preheated.  Gas 
generated  leaves  at  a  and  passes  through  tubes  in  the  vaporizer  b. 
These  tubes  are  surrounded  by  water  which  is  thus  heated,  and  the 
steam  formed  goes  to  the  ashpit  through  the  pipe  c.  Water  utilized 
in  the  vaporizer  is  generally  the  exhaust  cooling  water  from  the 
engine.  Its  heat  is  thus  retained. 

Gas  as  it  emerges  from  the  generator  is  too  hot  for  use  in  the 
engine.  It  is  cooled  in  the  vaporizer,  first  to  reduce  its  volume, 
second  to  prevent  back-firing.  From  the  vaporizer  the  gas  goes  to 


GAS  PRODUCERS 


130  INTERNAL  COMBUSTION  ENGINE  MANUAL 

the  scrubber  through  the  seal  box.  The  water  level  shown  in  the 
box  is  that  when  the  engine  is  running.  When  the  engine  is  stopped 
the  water  overflows  from  the  scrubber  to  the  seal  box  until  the 
water  level  rises  above  the  level  of  the  bottom  of  the  partition.  This 
forms  a  water  seal  and  prevents  gas  in  the  scrubber  and  purifier 
from  backing  into  the  generator  when  the  engine  is  stopped. 

The  scrubber  is  a  cylindrical  receptacle  filled  with  coke.  A 
water  spray  keeps  this  constantly  wet.  The  gas  flows  in  the  oppo- 
site direction  to  the  water  and  the  latter  cleanses  the  gas  of  all  the 
entrained  tarry  vapor  and  dust,  depositing  these  on  the  coke.  The 
gas  leaves  the  scrubber  by  a  pipe  which  leads  to  the  purifier.  This 
is  a  receptacle  containing  several  layers  of  sawdust.  Here  the  gas 
is  dried  and  any  small  amount  of  tar  or  dust  which  escaped  the 
scrubber  is  removed.  From  the  purifier  the  gas  passes  to  the  engine. 

In  modern  practice  a  branch  pipe  leads  from  the  system  between 
the  scrubber  and  the  generator.  This  branch  leads  to  a  chimney 
and  contains  a  fan.  By  suitable  valves  the  gas  can  be  diverted  from 
the  main  line  and  sent  out  of  the  chimney  by  the  fan  mentioned. 
This  is  used  to  start  the  plant.  When  first  started  the  fan  supplies, 
the  suction,  since  the  engine  is  stopped,  and  the  gas  given  off  not 
being  suitable  for  use  in  the  engine,  is  allowed  to  escape  to  the 
atmosphere. 

Operation.  To  start  the  plant,  build  a  fire  on  the  grate,  charge 
the  generator  through  the  hopper,  open  the  valve  to  the  chimney 
and  close  that  to  the  engine.  » Start  the  fan.  Gas  will  now  be 
generated,  but  at  first  it  is  not  of  a  quality  to  use  in  the  engine. 
A  small  pet  cock  is  fitted  to  the  chimney  vent  for  testing  the  gas. 
When  this  is  of  a  suitable  quality,  shown  by  its  burning  at  the 
pet  cock  with  a  reddish  blue  flame,  open  valve  and  start  engine. 
After  a  few  revolutions  of  the  engine  the  plant  is  self  operative  and 
the  fan  can  be  stopped  and  the  chimney  valve  closed. 

To  stop  the  plant,  stop  engine,  fill  generator  with  coal,  and  open 
chimney  valve  enough  to  supply  just  sufficient  air  to  maintain  a 
fire.  The  chimney  valve  and  valve  to  the  engine  are  generally  so 
arranged  that  closing  one  opens  the  other. 


GAS  PRODUCERS 


131 


The  Generator.  The  generator  is  in  effect  a  large  steel  furnace, 
fire-brick  lined,  with  a  grate,  ashpit,  etc.  A  hopper  is  fitted  at  the 
top  through  which  the  'fuel  can  be  supplied  without  stopping  the 
engine.  It  is  belled  at  the  top  as  seen  in  Fig.  84  to  create  a  gas 
circulation.  If  the  gas  were  drawn  off  at  the  top  of  the  furnace  it 
would  contain  a  large  percentage  of  the  volatile  gases  of  the  fuel. 
These  are  high  in  tarry  vapors  and  ammonia.  By  diverting  these 


FIG.  84. — Combined  Generator  and 
Vaporizer. 

gases  back  through  the  hot  bed  of  fuel  by  the  belled  top,  they  are 
partially  decomposed  and  form  CO  and  H2.  Sometimes  a  syphon 
injector  is  fitted  to  the  top  of  the  generator  for  this  purpose. 

Many  plants  have  the  vaporizer  built  into  the  top  of  the  generator 
as  shown  in  Fig.  84.  A  means  is  also  frequently  provided  for  pre- 
heating the  air.  This  is  essentially  foreign  practice.  The  hot 
gases  from  the  fuel  bed  circulate  around  the  passage  (7.  The  water 
in  V  is  heated  by  this  means  and  by  contact  with  the  fuel  chamber 
partition.  Air  entering  at  A  picks  up  the  steam  formed  in  V  and 
carries  it  to  the  ashpit  through  B. 


132 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


Vaporizer  or  Economizer.  When  the  gases  leave  the  generator 
their  temperature  is  too  high  for  use  in  the  engine  and  they  must 
be  cooled.  To  prevent  waste  of  heat  taken  from  them  during  this 
cooling  process,  upon  leaving  the  generator  they  are  passed  through 
the  vaporizer  or  economizer,  where  some  of  the  heat  is  given  up  to 
the  air  or  is  utilized  to  form  the  steam  used  in  the  generator.  As 
shown  in  Fig.  84  the  vaporizer  and  economizer  is  built  into  the 


Gas 


PIG.  85. — Vaporizer. 


FIG.  86. — Combined  Vaporizer  and 
Economizer. 


generator.  If  a  separate  unit  the  vaporizer  takes  the  form  shown 
in  Fig.  85.  Fig.  86  shows  a  combined  vaporizer  and  economizer, 
which  forms  the  necessary  steam  and  preheats  the  air  simulta- 
neously. Within  the  main  shell  is  mounted  a  concentric  flue  having 
spiral  ribs  around  the  outside.  The  hot  gases  pass  down  the  central 
flue;  water  fed  to  the  spiral  ribs  is  vaporized  by  the  heat  from  the 
gases,  and  air  passing  between  the  ribs  and  shell  is  heated  and  at 
the  same  time  picks  up  the  steam  formed  and  carries  it  to  the 
ashpit. 


GAS  PRODUCERS 


133 


The  Scrubber.  After  passing  through  the  vaporizer,  or  upon 
leaving  the  generator,  if  of  the  form  shown  in  Fig.  84,  the  gases 
next  go  through  the  scrubber.  This  serves  to  cool  them  further 
and  principally  to  remove  the  tarry  vapors  and  minute  particles 
of  dust,  ash,  grit,  etc.,  which  they  have  picked  up  from  the  fuel 
in  the  generator.  The  wet  scrubber  is  a  cylindrical  shell  almost 


FIG.  87. — Coke  Pilled  Scrubber. 


Power 

FIG.  88. — Lattice  Filled  Scrubber. 


filled  with  crushed  coke  or  with  wooden  grids.  It  contains  a  water 
spray  at  the  top  which  keeps  the  coke  covered  with  a  cool  film  of 
water  at  all  times.  As  the  gases  pass  up  through  the  filling  of  the 
scrubber  they  come  in  contact  with  the  wet  surface  of  this  "  filling  " 
and  deposit  the  impurities  thereon.  Fig  87  illustrated  a  coke  filled 
scrubber  and  Fig.  88  a  lattice  filled  one.  The  gases  entering  at 
the  bottom  of  the  scrubber  pass  through  the  pool  of  water  formed  by 
the  spray.  The  gas  pipe  mouth  is  below  the  surface  of  the  water 
and  as  the  gases  pass  through  this  water  the  larger  impurities  are 
removed.  The  gases  pass  out  at  the  top  to  go  to  the  dry  purifier. 
10 


134 


INTERNAL  COMBUSTION  ENGINE  MANUAL 


The  Purifier.  The  dry  purifier  is  practically  a  filter,  consisting 
of  a  box  filled  with  sawdust,  excelsior,  or  similar  material.  Here 
the  gas  is  dried  and  any  impurities  that  escaped  the  scrubber  are 
removed.  The  gases  enter  from  below  the  excelsior,  which  is  sup- 


FIG.  89. — Dry  Scrubber  or  Purifier. 


Coke-filled 
Wet  Scrubber 


FIG.  91. — Suggested  Form  of  Spray  Nozzle.        FTG.  90. — Combined  Wet 

and  Dry  Scrubber. 

ported  on  shelves,  pass  through  the  filler  and  out  the  top  to  the 
engine.  A  dry  scrubber  is  shown  in  Fig.  89.  In  some  cases  the  puri- 
fier and  scrubber  are  combined  as  shown  in  Fig.  90.  Much  trouble 
has  been  experienced  in  getting  a  spray  nozzle  that  would  cover  the 
coke  evenly.  The  form  shown  in  Fig.  91  has  been  suggested.  The 
holes  in  an  ordinary  spray  nozzle  clog  easily  and  the  result  js  a 


GAS  PRODUCERS  135 

deficient  water  supply.  In  the  type  suggested  the  spray  pipe  open- 
ing is  reduced  to  about  f  inch  by  a  bushing.  As  the  water  emerges 
from  this  in  a  solid  stream  it  falls  upon  a  shallow  saucer  supported 
from  the  delivery  pipe  by  a  bracket.  This  should  give  an  efficient 
spray  that  cannot  become  clogged. 


136  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Pressure  Producers 

In  the  pressure  producer  air  and  steam  is  forced  through  the 
fuel  bed  by  a  fan  or  blower,  and  the  ashpit  is  generally  of  the  closed 
type.  Steam  for  the  generator  is  generally  furnished  by  a  separate 
boiler,  and  since  the  production  of  gas  is  not  regulated  by  the  de- 
mand as  in  the  suction  type,  a  gas  holder  is  usually  necessary.  No 
vaporizer  is  present  when  a  separate  boiler  is  used,  but  an  econo- 
mizer is  usual  for  preheating  the  air.  As  the  ashpit  is  of  the 
closed  type,  it  is  necessary  to  make  provision  for  removal  of  ashes 
without  stopping  the  generation  of  gas. 

A  schematic  plan  of  a  pressure  producer  is  shown  in  Fig.  92.  A 
is  a  small  steam  boiler  for  making  steam  and  producing  the  neces- 
sary air  pressure;  B  is  the  generator;  C  is  the  economizer  with 
superheater  and  wash  box ;  D  is  the  scrubber  and  E  the  purifier ;  F 
is  the  gas  holder,  consisting  of  a  steel  tank  supported  by  guide 
framing  upon  which  it  travels  up  and  down.  The  fan  or  blower  is 
interposed  between  the  generator  and  economizer  in  the  air  line. 
The  drips  shown  are  for  the  removal  of  water  from  the  gas. 

In  operation,  the  gases  generated  in  the  producer  enter  the  super- 
heater and  economizer.  Here  the  gas  preheats  the  air  to  be  used 
in  the  generator.  The  gas  passes  through  the  economizer  and  the 
wash  box,  depositing  a  large  portion  of  its  extraneous  suspended 
matter.  This  wash  box  acts  as  a  seal  or  non-return  for  gases  stored 
in  the  holder  and  present  in  other  parts  of  the  system.  From  the 
wash  box  the  gas  enters  the  scrubber,  goes  to  the  purifier  and  finally 
enters  the  holder  which  stores  up  a  supply  sufficient  for  starting  and 
running  for  several  minutes.  The  chief  function  of  the  holder  is 
to  regulate  the  pressure  and  variations  in  consumption  and  mixture 
of  the  gases. 


GAS  PRODUCERS 


137 


138  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Combination  Producers 

The  combination  producer  plant  is  very  similar  to  the  pressure 
type,  the  elements  being  the  same.  The  fan  or  blower  is  inserted 
between  the  generator  and  the  engine,  generally  just  after  the 
scrubber,  thus  putting  the  generator  under  suction  and  the  re- 
mainder of  the  plant  under  pressure.  Many  plants  are  of  the 
double  producer  type,  two  generators  being  used  in  parallel.  The 
Loomis-Pettibone  is  an  example  of  this  type,  Fig.  93. 

Generators.  The  unit  consists  of  two  generators,  cylindrical,  of 
iron  and  steel,  lined  with  fire  bricks,  with  arches  at  the  bottom  to 
support  the  fuel.  Charging  and  the  admission  of  air  is  provided 
for  by  doors  at  the  top.  Two  cleaning  doors  above  the  arches  and 
one  below,  opening  into  the  ashpit,  are  provided.  Steam  connec- 
tions are  made  from  the  boiler  to  the  ashpit  and  to  a  point  above 
the  fires  in  each  generator. 

Boiler.  The  boiler  is  of  the  multi-tubular  type  and  connected 
at  the  base  with  the  generators  by  means  of  brick-lined  flues.  These 
connections  are  controlled  by  the  water  cooled  valves  A  and  B.  All 
the  hot  gases  pass  through  the  boiler  from  the  generator  and  give  up 
a  large  proportion  of  their  sensible  heat,  thereby  producing  steam, 
which,  in  turn,  is  used  in  the  fires  of  the  generator. 

Wet  Scrubber.  This  is  of  the  coke  type,  the  coke  being  carried 
on  trays. 

The  Exhauster.  This  is  a  blower  in  the  line  between  the  wet 
scrubber  and  the  dry  scrubber.  It  maintains  sufficient  vacuum  on 
the  fires  to  create  a  down  draught  through  the  fires,  and  sufficient 
pressure  to  deliver  the  gas  to  the  holder. 

Valves  C  and  D  control  the  course  of  gas  delivered  by  the  ex- 
hauster. The  purge  stack  valve  C  is  only  opened  when  starting  the 
plant,  and  valve  D  is  on  the  line  to  the  dry  scrubber.  When  one  is 
opened  the  other  is  closed. 

The  Dry  Scrubber.  The  dry  scrubber  is  of  the  usual  type,  except 
that  it  consists  of  two  chambers  so  arranged  that  one  can  be  cleaned 
while  the  other  is  in  operation. 

The  gas  holder  is  of  the  standard  type. 


GAS  PRODUCERS 


139 


140  INTERNAL  COMBUSTION  ENGINE  MANUAL 

Operation.  Fires  are  kindled  with  coke  and  wood  in  the  genera- 
tors to  a  depth  of  about  four  feet,  the  exhauster  creating  a  down- 
ward draught,  with  top  doors  H  and  I,  and  valves  A,  T>,  G  and  C 
open,  and  valve  D  closed.  As  soon  as  the  fires  are  thoroughly 
kindled,  steam  is  admitted  into  the  top  of  the  generators  at  F  and 
E,  and  mingles  with  the  air  admitted  through  top  doors  H  and  I, 
which  the  operation  of  the  exhauster  draws  down  through  the  fresh 
charge  of  coal  and  then  through  the  hot  fuel  bed  beneath.  The 
resultant  producer  or  generator  gas  is  drawn  down  through  the 
grates  and  ashpits  of  generators  1  and  2,  valves  A  and  B  being 
open,  passes  up  through  the  vertical  boiler,  and  so  on  through  valve 
G  to  the  scrubber  and  exhauster.  Valve  C  is  then  closed  and  valve 
D  opened,  and  the  gas  is  driven  through  the  dry  scrubber  to  the  gas 
holder. 

Coal  is  charged  through  the  open  top  doors  as  needed. 

The  making  of  gas  is  according  to  the  demand,  as  the  speed  of 
the  exhauster  is  automatically  regulated  so  as  to  keep  the  holder 
full. 

The  charging  doors  being  open  while  the  air  is  passing  down 
through  them,  the  operator  can  see  the  exact  condition  of  the  fires 
and  charge  the  coal  to  such  parts  of  the  fires  as  most  need  it,  thereby 
avoiding  the  necessity  for  poking  the  fires. 

The  condition  of  the  fires  is  regulated  by  occasionally  passing 
steam  up  through  one  generator  and  down  through  the  other  for 
a  fraction  of  a  minute.  This  is  accomplished  by  closing  the  top 
doors  and  valve  B  and  introducing  steam  at  J.  The  steam  is  in- 
troduced alternately  into  generators  1  and  2  by  using  alternately 
the  valves  A  and  B  and  steam  inlets  J  and  K. 

When  bituminous  coal,  wood  or  other  fuels  containing  tar  and 
volatile  matters  are  used  in  these  generators,  all  the  gas  and  tarry 
matters  distilled  from  the  fresh  fuel  in  the  upper  strata  of  the  fire 
pass  down  through  the  deep  fuel  bed,  the  resultant  gas  being  fixed 
and  free  from  tar. 

Experiments  have  been  made  on  two  generators  connected  in 
series,  this  with  the  object  of  removing  the  tarry  vapors  generated 
in  the  first  unit  by  decomposition  in  the  second.  No  practical 
plant  of  this  type  is  now  in  use. 


GAS  PRODUCERS  141 

Advantages  of  the  Various  Types 

The  suction  type  of  producer  is  simpler  and  cheaper  than  the 
pressure  type.  It  requires  no  boiler  for  generating  the  steam 
needed  (this  is  not  an  advantage  in  all  cases  as  some  pressure  pro- 
ducers generate  their  steam  by  a  vaporizer  built  into  the  generator), 
no  gas  holder  is  required,  and  the  proportion  of  steam  and  air  that 
is  admitted  to  the  generator  is  under  control,  hence  less  trouble  is 
experienced  with  clinkering.  The  amount  of  gas  produced  is  regu- 
lated by  the  engine.  The  washing  apparatus  is  much  simpler  and 
cheaper.  As  the  plant  is  under  a  slight  vacuum  a  leak  will  not 
cause  a  loss  of  gas;  instead  a  small  amount  of  air  will  enter  the 
plant.  It  requires  less  attention  than  the  pressure  plant. 

The  two  principal  advantages  of  the  pressure  type  are :  (1)  it  can 
produce  gas  more  cheaply  than  the  suction  type,  and  (2)  very  poor 
grades  of  fuel,  even  slack  and  peat,  can  be  used,  whereas  the  suction 
type  as  manufactured  in  this  country  requires  the  best  quality  of 
coal  or  coke. 

Gas  can  be  produced  more  cheaply  by  the  pressure  than  the  suc- 
tion system  because,  when  using  the  former,  valuable  by-products 
are  recovered  which  cannot  be  saved  in  the  suction  producer.  The 
value  of  ammonia  alone  which  is  recovered  reduces  the  cost  of  pro- 
duction to  such  an  extent  that  pressure  producer  gas  can  be  manu- 
factured and  sold  at  a  profit  for  less  than  five  cents  per  1000  cubic 
feet. 


INDEX. 


PAGE 

Acetic  acid  in  cylinder 10 

Acetylene,  use  in  engines  of.  14 
Admission,    best    temperature 

for     48 

Advanced  spark    76 

Advantages  of  compression .  .  40 
Advantages,  relative  of  steam 

and  I.  C.   E 18 

relative    of    two    and    four 

cycle   37 

After  burning   90 

Air  cooling  66 

Alcohol     10 

advantages  of   11 

carburetion  of  49 

denatured    10 

engine 122 

thermal  efficiency  of 11 

Alco-vapor  engines  122 

Atomizing  vaporizers    49 

Back  firing    73,  86 

Balancing  crank  arms 29 

Beau  de  Rocha's  principle...  21 

Blast   furnace   gas 13 

Blowing     88 

Booster    54 

Carbon  deposits,  knocking  due 

to     88 

premature  ignition  due  to..  88 

Carbureter    42 

defects    89 

double   float  type 50 

requirements  of  good 44 

Schebler    44 

Carburetion  defined   42 

of  air   42 

of  alcohol    49 

of   gas    43 

of  gasoline 43 

of  kerosene    48 

of  oil    51 

spray     44 

surface  43 

Carburizer     42 

Cards,  indicator    -. .  74 

Charge     42 


PAGE 
Classification     of     I.     C.     E., 

cyclic     34 

thermodynamic     39 

Clearance    15,  90 

Coil    windings,    four   cylinder 

ignition    54 

one  cylinder  ignition 52 

Coke   oven   gas 12 

Combustion,   rate  of 15 

Compounding  the   I.   C.   E...     20 
Compressed   air,   starting  by, 

83,  106 

Compression     15,  34,  40 

efficiency  depends  upon.  ...     82 

limits  of    41 

lost    88 

Connecting  rod    27 

Constructional  details    23-33 

Cooling  cylinder  by  air 66 

water    64 

Cooling   gases    64 

system  17,  64 

valves,   pistons,   etc 65 

Countershaft     33 

Cracking  process    7 

Crank  chamber  explosions...     88 

Crossley  vaporizer   49 

Crude  oil   10 

Cut-off    15 

Cycle  defined   34 

Cycle,   Diesel 116 

four   or   Otto 34 

theoretical    75 

two  or  clerk 34,  36 

Cylinders  23 

air  cooled  23,  66 

copper  jacketed  24 

en  &Zoc  24 

two  cycle 25 

water  cooled    23 

Defects  in  operation,  common.  86 

Deflegmator    6 

Development  of  the  I.  C.  E. . .  20 

Diesel  engine  114 

cycle    116 

valve  group    118 

Dissociation  theory   90 


144 


INDEX 


PAGE 

Distillates,  heavy   10 

Double  acting  engines. 38,  95,  104 
Dual  ignition  60 

Economizer     132 

Effect  of  heat  before  compres- 
sion        83 

Efficiency    depends    upon    de- 
gree of  compression 82 

Efficiency,    thermal    of    steam 

and   I.  C.  E 82 

Engine,  acetylene 14 

alcohol    122 

alco-vapor    122 

Diesel  oil 114 

Gnome  aeroplane    106 

Jaeger  launch 122 

Knight  slide  valve 108 

Koerting  two  cycle  gas....     95 

losses  in  the 18 

Mietz  and  Weiss  kerosene. .   113 

multicylinder   91 

Standard  double  acting....   104 

Sterling    100 

Twentieth  Century  launch .   119 

Engler's   experiment    4 

Exhaust,  underwater 33 

Exhauster    138 

Explosions,  admission  pipe.  . .     86 

carbureter     87 

crank  chamber    88 

muffler    87 

weak   87 

Flame  propagation,  rate  of .  . .  15 

Float  valve  carbureter 44 

Fly  wheel   29 

Fractional  distillation 5 

Fuel,  classification  of 1 

considerations  governing  se- 
lection of 1 

gaseous    11 

heating  values  of 1-13 

liquid    4 

oil  10,  51 

solid    2 

system    16 

Gas,  acetylene  14 

air   2 

blast  furnace  13 

calorific  value  of 1-3,  11-14 

coke  oven 12 

illuminating   12 


PAGE 

natural     13 

oil    11 

producer    3,  126 

water    2 

Gasoline    8,  43 

volatility  as  test  for 9 

Generator  131,  138 

Gnome  engine   106 

Governing  by  adjustable  spark.     73 

combination  systems  74 

exhaust     74 

hit  and  miss  system 69 

throttling 72 

variable  mixture 72 

varying  compression   74 

Governor,  pick-blade   71 

Governors  and  governing 69 

Hammer  break  igniter 59 

Heat  balance   18 

Heat  engine  efficiency 82 

Horse-power,  brake 78 

indicated,  how  obtained. ...  78 

Hot  tube  ignition 62 

Ignition    16,  35,  52 

by  heat  of  compression 63 

comparison  of  different  sys- 
tems of   60 

dual    60 

early   76 

electric  52 

faulty    85 

four  cylinder   54 

hammer  break 59 

hot  tube 62 

jump   spark    52 

late    76 

make  and  break 57 

multicylinder   54 

premature    41,  88 

wipe  spark   58 

Ignition  plugs    52,  58,  59 

Ignition  wiring 52,  54 

Indicators  for  I.  C.  E 78 

Indicator  cards   74 

charge  throttled   75 

faulty  admission 77 

faulty  exhaust  77 

ignition  advanced 76 

ignition  retarded    76 

normal    75 

two  cycle  78 


INDEX 


145 


PAGE 

Internal  Combustion  Engines — 

for  aeroplane  use 20,  106 

for  battleship  use 21 

for  marine  use.. 21,  100-106, 

114-123 

Jacket,  water,  temperature...     20 

Jump  spark  coil 53 

Jump  spark  ignition 52 

Kerosene    9 

carburetion  of  48 

engine    113 

Knight  slide  valve  motor 108 

Knocking,  spark,  gas,  and  car- 
bon         88 

Koerting    double    acting    gas 

engine    95 

La  Costa  timer 56 

Late  ignition  76 

Liquid  acetylene  14 

Long  and  short  stroke 89 

Losses  in  the  I.  C.  E.  and 

steam  engine  19 

Lowe's  method  12 

Lubricating  oil,  requirements 

of  good 67 

Lubrication  66 

Lubricators  67 

Lunkenheimer  mixing  valve. .  47 

Magneto,  high  tension 54 

low  tension 54 

with    automatic    spark    ad- 
vance      107 

Make  and  break  ignition 57 

Management  83 

Manograph    78 

Master  vibrator 61 

Mechanical  ebullition   43 

Medium    42 

Mietz  and  Weiss  kerosene  en- 
gine    113 

Misfiring,  continuous 86 

intermittent    87 

Mixing  valve 42,  44 

Lunkenheimer   47 

Mixture,  lean  and  rich 15,  42 

Muffler    29 

ejector    31 

explosion   87 

gas  pipe  31 

Thompson   30 

Multicylinder  ignition 54 

Multicylinder  timer 55 


PAGE 

Naphtha  engine 122 

Natural  gas    13 

Normal  indicator  card 75 

Oil,  cylinder  lubricating 67 

fuel    10,  51 

gas 11 

ring 68 

Operation   83-86 

Overheating    87 

Petroleum  products  8 

Petroleum,  source,  formation, 

and  composition  of 4 

refining    5 

Phases  in  four  cycle  engine..  34 

Phases  in  two  cycle  engine..  36 

Pick-blade  governor 71 

Pintsch  oil  gas  producer 11 

Piston 25 

head,  two  cycle  type 27 

lubrication    67 

Plug,  spark 53 

Premature  ignition 41,  88 

Pressure  diagram  91 

Pressure  gas  producers 136 

Producers,  gas  126 

advantages  of  various  types .  141 

classification  of 128 

combination    138 

for  marine  use   126 

fuels  used  in 126 

Loomis-Pettibone,   138 

Loomis-Pettibone,  operation 

of  140 

pressure     136 

pressure,  operation  of 136 

reactions  in    126 

suction  128 

suction,  operation  of 130 

Pump,  gas   37,  98 

oil    114 

water    64 

Purification  of  petroleum  dis- 
tillates      6 

Purifier    134 

Push  rod  28 

Ratio  of  expansion 15 

Reduction    gear    for    counter- 
shaft     32 

Residuum    6 

Reversing    124 

Rings,  piston  25 


146 


INDEX 


PAGE 

Scavenging  the  cylinder 91 

Scrubber,  combined,  wet  and 

dry    134 

wet,  coke  and  lattice 133 

Secondary  spark  gap 92 

Shaft,  crank  103 

Smoky  exhaust   88 

Spark  coils 53,  54 

Spark  plug  53 

Splash  system  of  lubrication . .  67 

Splitdorf  timer   55 

Spray  carburetion 44 

Spray  nozzle  for  scrubber 134 

Standard  double  acting  gaso- 
line engine  104 

Start,  failure  to 84 

Starting  an  I.  C.  E 83 

Starting  on  spark 84 

Still,  horizontal  American 5 

Stopping  an  I.  C.  E 83 

Straining  gasoline   89 

Stratification  theory 90 

Submerged  exhaust  33 

Suction  producer 128 

Surface  carburetion  .  43 


PAGE 

Temperatures  at  which   frac- 
tions distill 7 

Three  point  suspension   103 

Thermo-syphon  system 65 

Timer,  La  Costa 56 

Splitdorf    55 

Trouble  hunting  85 

Types  of  I.  C.  E 38 

Vacuum  process   7 

Valve  gears    28,   32 

Valves    27 

requirements  of  efficient...  28 

rotary  28 

slide 28 

Vaporizer,  fuel 49 

gas  producer 132 

Water  cooled  engine 64 

Water  cooled  valves,  pistons, 

etc 65 

Water  gas  2 

Water  jacket   24 

Weak  explosions  87 

Wipe  spark  igniter 58 

Wrist  pin 27 


THIS  BOOK  IS  DUE  ON  THE  LAST  DAT] 
STAMPED  BELOW 

AN  INITIAL  FINE~OF  25  CENTS 

OVERDUE. 


OCT   8     1935 


LD21-100m-7,'33 


•J*i 

- 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


